As others have already said, the mark-up on bikes is not high. You may see large discounts, but they will be on a.) bikes that have been around awhile and are not moving, or b.) closeout bikes that were purchased by the shop at a big discount and are not moving.

Your best bet for getting a deal is to be a good customer. Be polite, buy stuff at the marked price, and don't try to haggle on everything (As an LBS employee, I HATE it when I see the "hagglers" coming in. Especially if they are driving a really expensive car...). If you come in often enough and are nice to us, we're more likely to cut you a deal when we can. But, as I frequently tell my customers, if you are waiting for the 50% Off Sale" you'll be waiting a long time, because it's never going to happen.