I think you could legitimately increase the price on steam to 10$. Comparing to Factorio and Automation Empire (25€!!), it's a fair price. Plus you could join sales, which seems to be an important part for games nowadays. Just my thoughts, don't expect you to follow them or anything.
Btw, I had difficulties paying and even donating on itch.io. I guess I will just have to buy it on steam aswell...