The difference is that with premium scripts being so cheap per hour, the chance of someone using the script for 30 hours (The amount of time it would require to earn $1 at $0.04/hr) is minimum. The guarentees that you atleast get a small amount regardless as to if they use it for 5 hours or 30.
Over-all you will be profiting more, as the average user will not spend 30+ hours using your script. However, if they do use it for more than 30 hours, you didn't gain anything extra, however if they're the casual botter, or just wanting to try it out, and uses it for 2-3 hours, you've gained quite a bit.
To say I'm dismissing the pros of other options is false. I'm caught between PPI and the one I suggested. PPI would be nice, and it wouldn't effect me very much, but I feel like it would turn into *cough* another platform and we will see low-quality scripts for $10-$20.
Granted, if they're kept clean PPI would by far be the best option.
