Not sure of the type of person you are, but it seems that most people that swear that they are going to get into shape with a big expenditure dont end up following through with the workout part of it. I needed to change up my cardio and told myself I was gonna swim, so I swam twice, decided I needed googles, bought a sweet pair of $15 ones, and ended up swimming twice more.
I would recommend getting a membership at a gym for a month and see how consistently you ride the workout bikes there. If after a month or two you are still riding the stationary bike 2-3 times per week, go ahead and make the investment in a real one for more money.
Again I dont know your personality but it just seems like everyone that spends a bunch on bikes or workout equipment never uses it, just trying to make sure you dont waste your money.