Agreed, it's expensive and slow. One exemple, DigiWeb will cost you €600 for installation/equipment, and €35 a month for 3.6MB download/ 384k upload with a 2.4GB cap.
Why are you considering it? Are you in a very remote location? If you already have satellite TV, you will require planning permission to erect a second dish.
thos is spot on Satellite can have massive latency and contention can run into the 100's:1
There are cheaper packages available than Digiweb, like skyadsl, but again hard to know what service will be like
where are you based?