Try a local towbar installation company in your area, see yellowpages, these should be far more competitve than the dealership. Dealerships tend to rip customers off with the extra add ons, way cheaper to tint windows etc rather than the dealership prices 

Thats exactly what i did when i bought my Camry station wagon five years ago. It ended up costing $300 all up to have the towbar fitted, and the trailer lights connector wired. I almost considered going to the toyota dealership first and getting one from them.. so glad i didnt now!!