From what I can tell, you cannot have an appointment less than 2.5 hours, which with the service fee works out to $55. While this is still cheaper than Exec, I do not think that 2.5 hours of cleaning is necessary every other week for a <500 square foot studio.
The price isn't bad, but I would be more comfortable if they didn't stick to "$20/hour" and instead did something along the lines of "$50 for a basic hour-long cleaning, including travel and cleaning fees, and only $20/hour for every additional hour."
I don't see the problem. You're just asking to pay more? If they're done in two hours, they'll either charge you less or leave, so you pay $55. In your example, that two hour cleaning is now $70. Additionally, I think you're underestimating the amount of time a good cleaning can take, even of a smaller apartment / studio.
The price isn't bad, but I would be more comfortable if they didn't stick to "$20/hour" and instead did something along the lines of "$50 for a basic hour-long cleaning, including travel and cleaning fees, and only $20/hour for every additional hour."