I just looked up a random ASIC, it consumes 1350W and costs 2500$. If you would buy an electric heater, you could get one for 50$. ASICS produce heat, but are not made for heating. ...but the PCB inside can release some nasty stuff, so it is not advised to use it as heating.
The reason ASICs cost so much is because of the upfront designing, tape-out, and testing costs and because they can get away with it because bitcoins are so valuable. The actual costs of making ASIC's are very cheap after the design if completed(few dollars per wafer dependent upon the quantity).
There is nothing wrong with using PCB's in heating if the right materials are used.
Economics will force either ASIC manufacturers themselves to start introducing these products or we will crowdfund the operation directly to force them to start and compete with these products.