That pricing looks very much "what it costs to run the service, plus some profit margin".
A service run by anyone with any business acumen will charge what customers will pay, modified for benefits that customer brings the company (like referrals, bigger revenue leading to a higher company valuation, etc.).
None of that depends on the frame rate or resolution.
I'm guessing the OP aims at professional, high-quality video editing rather than at a hobby use. Which is probably the right thing to do as there are low-quality free options already. Hard to compete with that.
> Up to 30 fps: Base price
> 30-60 fps: Base price × 2
> 60-90 fps: Base price × 3