The shop would seem to be going to extraordinary measures to make you happy by special ordering a bike at your request and not taking a deposit. If you don't like the bike don't buy it, definitely. They are taking a risk to make a customer happy. Unless they are able to group this with a larger order to earn free freight, they are likely spending $30 or so to get the bike. That's hard cost that they will not recoup if you don't buy. That doesn't mean you owe them anything but it seems like extraordinary service at this point.