Why are their no cheap wifi thermostats?
Simple programmable thermostats use so little energy that they can run a meaningful amount of time on batteries.
WiFi requires a considerable energy budget.  That characteristic of WiFi is why Bluetooth was created, to make earbuds, headphones etc. possible.  You'd have to change batteries twice a week if you had a battery powered WiFi thermostat!
As such, a WiFi thermostat needs to have a means to sap its own internal power needs off of the power going to the furnace etc.  That's actually a bit tricky, especially to get past regulators (i.e. to have a TUV, BSI or genuine, earned CE mark.)
Also, you are comparing apples and oranges.  Many of the &quot;WiFi smart plugs&quot;  you are seeing are cheap Cheese junk that is direct-imported, or direct-imported using Amazon's warehouses as a free-trade zone drop ship point.  The upshot is that the CE certification is worthless and faked.  That the item has earned its CE mark is the responsibility of the importer.  That's you. If you got it from Amazon, don't look at them - they insist they're &quot;just a platform&quot; for the third party seller you actually did buy the item from... And that seller has no presence in Europe, so not responsible for safety compliance.
Apparently our far-Eastern communist buddies are not that keen on offering dirt cheap WiFi smart 'stats for sale, or else they'd hit your price point too, I'm sure.  Probably for the best.