It's tricky to keep the price stable in sats when the BTC-USD exchange rate is so unstable, at least as long as your customers are all pricing their consumption in dollars.

Your prices could increase or decrease 2% on a typical day, and would on average get more expensive over time. Not to mention the flash crashes which involuntarily put your product on sale.

As more people keep larger stacks of sats in reserve, this will become less of a problem.