I would like to turn a certain PDF into a .jpg and I do not anticipate a need to do this again in the near future. Seems a little out of touch to expect anyone to pay $15.00 for a month and “potentially” hundreds of dollars to use a service only once or twice in a year.
On your most economical plan, Adobe receives about half of a dollar per day and allows an unlimited number of document conversions , as well as other services.

Adobe should offer an alternative payment schedule of $1.00 per document,
up to, $3.00 for a 24 hour day of unlimited use.

This would be much more inviting to the casual customer and there is a high likelihood of more than 1,000 people per day wanting to use a pay-per-use service rather than long term commitments.