That's why there are rental BC's. If your shop does not have enough of a selection tell them. Or go elsewhere. A BC is a big ticket item. Few shops can carry one or more of each size and afford to allow someone to buy it and then take it back just because they don't like it.
You cannot compare it to something like a mask. I have a try and return policy on masks as long as it's not broken, scratched, or otherwise messed up. Try it in the pool a few times and if it does not work send it back for a refund minus shipping or exchange for another model. I can then use it in my classes or sell it as a demo unit and afford to take a small loss.
BC? nah. Once you put it in water it loses about 50% of it's value in my mind. I don't know how many times you had it in the water, what kind of water, how well you rinsed it out, etc..
And you can't compare it to a car. Dealers have specific demo models. And truth be told most test drives end up in some kind of sale. Car dealers are also much larger and there are a lot more of them than dive shops.
Do your homework, get some unbiased opinions, and so what it you don't exactly like the model you choose. Learn to dive it and learn to make it work.
Or just buy a BPW and set it up the way you want it. If you decide you don't like it the resale value is going to be much better than a jacket or back inflate. But unless it's defective don't plan on being able to give it back or trade it in for full value.
---------- Post added November 17th, 2013 at 11:31 AM ----------
I have never seen a store that will let me take a pair of shoes around the block and first. What would they do with the rejects. Don't know where someone's feet have been. That's just gross.