I've never seen fees like that, I'd move on to another property! We've done two fairly recent SPI trips and I've found very reasonable, beachfront rentals through AirBnB without fees like that, so it's definitely doable.
That's what happens when you buy a property and turn it over to a management company. You can either pay all their fees out of your profit, or you can let them charge the fees (but likely lose some bookings!)
As an owner, I think the most profitable option is to self manage if you have the time. But many people don't need the monthly income, they just want to break even. All those management expenses are deductible, so they end up paying little to no taxes on the rental income that way, and someone else's money is building equity.
Crappy for vacationers, though.