Things are waaaaay more expensive in August.. and accomodation is hard to find.
I really do not think 110 for a couple in August is that bad at all.
Prices do go down after August 25.. but you are going in the absolute peak time.
Also last year i went to formentera right at the beginning of September and it was absolutely PACKED. I did ride my bike away to a couple of beaches further away but it wasn't exactly calm and peaceful.
I would get booking.
I'm going to be there mid august, and will be on my own for a few days before I meet up with thers later. I decided to stay in San an for the first couple of days on my own, because anywhere in Pdb is just way too much. Then I'm moving over to pdb later....but as I go back and look at things.. many many places are all booked up!
Good luck in finding somewhere.. I really think that 110 per couple is not bad for that time of year.