Pricing via accounts might be suboptimal, but pricing by tickets? This way the useless tickets of people having problems with third party software and still asking me for help will hurt me even more.

Not only do they waste my time then, they also waste my money.

And if I wanted to annoy somebody I knew was using a pay-per-ticket account, I could quickly write up a small script to submit thousands of bogus tickets.

Charging for a resource entirely under control of others and not at all under your control seems to be a bad thing for me.