I agree about the servicing, keeping them in good condition will prevent them seizing, annually for me. I’ve only ever had one seize, that was on a Mk1 rear, I don’t think the previous owner had looked at them for sometime.
I could probably do you a pair on my 3D printer if your looking to save some money, they should be OK as long as you don’t go too fast?
I’m knitting a pair out of Kraft Cheese Slices, which would look the part when colour coded…
If you use pteg they may be even rated at 5mph 
I used Eurocarparts when I replaced my NC front calipers a couple of years back. I’m sure I paid around £60 each exchange when they had a deal on. Quality was good, and around 30 mins max per side to replace. Why even consider cheap ones at these prices?
Note, if you need one caliper, odds are you’ll need to replace the other one within a month or two, so might as well do both at the same time.
If it is too good to be true, it generally is too good to be true. Be weary of ‘cheap’ Chinese parts. There is a reason why they cost less. They are generally of inferior quality. OEM, or licensed after market parts, are a wiser and better choice.
I used the refurbished one supplied from autolink they are original mazda calipers, this can be seen by markings on the castings, they charge a refundable deposit on return of your old calipers ( as long as genuine mazda) you can even get them from their eBay site, about £85 I found them to be as good as new
I’m afraid I don’t trust anything Chinese. My son bought my wife a galvanised watering can the other day. It leaked, the chinese seem to run on the minimum quality they can get away with and it seems to apppy to all products. When you look at how things were almost over engineered in the past but lasted you realise that today we are going backwards…sorry for the rant. 
The only real question here is how much do you value your life and that of others. Don’t EVER take a chance with brakes. Go for either a genuine OEM part, of if that’s not affordable get a quality refurb OEM set from a reputable supplier. IMHO.
I’ve always relied on Andrew at Autolink for exchange remanufactured…for 16 years with both our 5’s.
Never disappointed bar 1 sticky unit which was sorted by return.
But Chinese made shock absorbers and springs, wheels, exhausts, radiators are ok…
There are multiple tiers of manufacture in every country. China is no different. We tap away on our Chinese made phones, tablets, laptops, staring at Chinese made TVs, drinking tea/coffee made using a Chinese made kettle, munching toast from our Chinese made toasters. If you are unfortunate to be admitted to hospital, take a look at some of the equipment around you. Some of it is Chinese branded. Even Western branded, such as Medtronic, will havde a complex supply chain that includes China. All of which works most of the time.
Autolink sold me a brand new brake caliper, non-OE, for 40 odd pounds. Came from China, via a UK stockist, I assume ok’d by Autolinkuk. I’ve had remanufactured calipers in the past, typically Brakes International. They last ok, but not as long as Sumitomo made originals, despite 90% of the caliper being Sumitomo. Where do the seals, pistons etc used by these companies come from?
Brakes International reman calipers come from Budweg, a Danish company. Actually Budweg has a JV with Shandong Longji, and makes calipers in Denmark, Korea and China. Digging into where 10p rubber seals and £1 pistons are made is tricky. I suspect the added value in Denmark is in assembly operations, rather than parts manufacture.
Of course, it might not matter where Budweg makes their seals, because you would trust Budweg to use suppliers that meet their appropriate construction standard.
There are the low tier suppliers, non-certified. Avoid them. Top tier will be locked into agreements with car manufacturers. Do your own due diligence on your suppliers, rather than focusing on where the parts are actually made. Don’t buy off Ebay.
I would caution against non-OE for rear calipers; here the manufacturers have appeared to made significant changes to the (problematic) Mazda-designed (actually not Mazda designed, its ripped off/licenced from from Lockheed-Girling) caliper adjustment mechanism, apparently to simplify it.
Unfortunately, it seems increasingly the problem these days that suppliers are lacking stock of remanufactured calipers, echoing the situation 22 years ago, when I literally had to send a set of rears to Budweg in Denmark for refurb, because there were no cores in the UK (at that time, Mazda were wanting £300 a caliper). But there might be different supply chain issues now.
i can only speak for myself here.
so its not where it is made that is the issue.
no,
the issue is ,does such a cheep item have a genuine certification!
lets be honest many of us have seen the documentrys and news items where people have ordered stuff to be made and have been asked if they want to pay extra for hooky certification marks and papers!
You are referring to counterfeit parts. ie. parts purporting to be from a recognised manufacturer, but they are not.
For instance, Mazda cooperated with Greek police on counterfeit Mazda branded oil filters. TUV paperwork is super easy to validate, if you are not sure if a part has genuinely received CE certification.
But there is another side. Mazda doesn’t like anyone but Mazda selling Mazda parts:
http://suppliers.mazdausa.com/Brand_FAQ.htm
20+ years ago, Mazda offered the MX5OC a very attractive deal; money pumped into the club, and Mazda taking care of the costs of the magazine. In return, the club keeping to the official line on grey imports (all imports are bad), a ban on future membership of Eunos Roadster owners (existing members be allowed to keep their membership), no promotion of businesses felt to be in competition with Mazda (selling Mazda parts, eg MX5parts, Moss). The offer was put to the membership, and rejected.
http://suppliers.mazdausa.com/Brand_FAQ.htm
Goes back to doing your own due diligence. As those bagain priced genuine new Mazda calipers really that?
The ad flagged by the OP throws up a few red flags as the seller don’t seem to be a transaparent business. Its not clear if they are a UK distributor (UK address) or a subsidiary (ad claims stock in UK, but indicates the parts ship from China).
Thanks to all for your words of wisdom (and occasional humour)
I will be steering clear of the advertised Chinese cheapies.
I’m not sure how to safely tell the difference between a low quality ‘knock off’ copy and a decent quality ‘pattern part’ ( for example, are the MX5parts new aftermarket callipers a safe buy? is NK a quality pattern part or cheap rubbish?), so will be going with remanufactured originals.
Of course, not all Chinese manufactured stuff is rubbish…
… sent from my Apple Mac - made in China!
NK I would say are kosher
https://www.nk-autoparts.com/en/about/matching-quality
And you will only get a years warranty on a recon part.
I bought brake cylinder seals for my 50 year old Hunter 2 years ago from PowerTrack Ltd so I’m pretty sure they would do them for the MX-5