Actually you asked no questions. The only question is in the title of your thread and even that doesn't clearly define the information you are looking for.
If your set on the idea that reliable thermostats can be achieved at low cost then by all means go ahead an use them on your animals.
I bought a helix for 130 dollars and it has worked like a charm for the last 4 years. Thats $32.50 per year so far on my investment and I expect to get many more years of use out of it. Not only this but I get the peace of mind that I'm using a tried and true product that has been proven effective for my application.
Is it possible that your thermostat could perform just as well? Sure, but I'm not willing to risk my animals to find out.