Last time I mentioned working with WF121 WiFi module. This module is manufactured by BlueGiga (now owned by Silicon Labs) and costs around $17 at digi-key if you need just one. One might ask why I am using this module, instead of say, ESP8266-based module that costs maybe $7 at same vendor?
I've discussed about this in past posts already, but this is worth repeating, this time with a bit more concrete example, especially now with new related legislation (EU directives) in effect.
The short answer is: Declaration of Conformity. To sell your devices in Europe you have to be able to present one. And some categories - like devices dealing with RF - require fairly strict examination before that can be (honestly) produced. As you might guess that examination costs a lot.
I am making a specialized, relatively low volume product in Europe I plan to actually sell. The original R&TTE (Radio & Teleterminal Equipment directive, 1999/5/EC) already places quite strict requirements on radio equipment, and new RED (Radio Equipment Directive, 2014/53/EC) makes those even stricter.
Let's say the one device I make sells, say, 1000 units over its product lifetime.
If I use pre-certified module, I don't have to re-certify my design (RF functionality) as long as I use the module as-is, antenna and all included, so total cost of the module is $17 (actually less, after proper sourcing and volume discounts are in.)
If use use ESP8266 module that is not pre-certified (so far I haven't seen even single module that were certified in Europe, but feel free to correct me if you know one), I actually have to certify my entire design as radio equipment myself. This is not cheap process - let's say I get lucky and the cost of RF certification is about 20k€ ($22.3k with today's rate), but it might be even more.
Suddenly that cheap module costs $7 + ($22300 / 1000) = $29.30 !
Not so cheap anymore.
And that is why I pay a bit more for certified RF modules.While for example EMC/EMI examination is still needed, that is very cheap compared to RF stuff. And those I have to do anyway.
One might get away for a while for selling devices that only claim to have been certified, but especially with new marking rules of RED, you only need one person who checks your claims and you are in deep s**t. Trust me, you do not want to risk it.
On the other hand, if you are building a hobby project you do not intent to sell (or considering the ambiguity of the phrase used in directive, "bring to market", even freely give away in some cases), feel free to use the cheap modules, hobby use doesn't carry such requirements. But you still need to be sure that the $3 module from china isn't actually (un)intentional emitter (aka jammer) - people are not happy if you happen to mess with their frequencies and hobby use doesn't give you free pass there if you get caught.
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