You got ripped off then - My father in law just rented a matrix for $165 per week for 2 weeks. You can get decent rates, you just have to know how to look.
Also - Bimmersport could strike up a relationship with the local rental shop. Recently, when I had my car repaired at atlantic autobody after an accident (great work, BTW), the rental agency was telling me how Atlantic only pays $20 per day. If they can set that up, so could bimmersport.