If the price was reasonable (less than ten cents in this case), absolutely.

I don't think you can charge so little. You'd probably have to buy some amount of runs in bulk.

Another alternative would be you buy access for a block of time, but not an auto renewing subscription. Mullvad VPN works like this, I have to go into the app and re-up if I want to keep using it every month.

However I think this type of app should be a one time purchase anyway. Looks to me like it could work without any server / hosted infrastructure.

This is actually a great idea. Lots of subscriptions just pay for a thing to be available. Netflix will tell you "sleeping giants" who never watch are ok, because the content was made available, but I think that's BS. I'd love to see a system where you're only billed on the months that you use it. Or even just charge me a dollar per use with a monthly cap of ten after which the rest of the month is free.