If you're folding on a laptop, you'll see between 60-90W usage. Converted to dollar's is roughly $60-90 annually on electricity, running 24/7.
If you have a desktop, the power at the wall could be anything from 80W on a small GPU, to 350W with a modern fast GPU.
If you pair up GPUs, it could be more than that.
Though not running fah, but boinc, I run at 1,7kWh for 6 GPUs 2x ryzen R9 CPUs and an Intel 6 core.
That's ~$1700 annually.
When I bought a new car, I could choose between a 30mpg fiesta St (200HP), or a V6 sedan doing 20mpg. The difference would net me $1700 annually on gas, so the savings I get with my car, I put in computing.