Don't Do it
DirectBuy may be worth it in the case you are building or furnishing an entire house. Their scam is something like this, you have to pay like $6000 to join, and then you get the discounts. All items will be shipped to a local warehouse and you will be responsible getting the items from there to your home. If you go for their free demo, seminar or whatever they call it, you will be forced to decide that day to join. If you decline you will forever be banned from DirectBuy (talk about high pressure).
Search google for DirectBuy and there are some forums that talk about it. I have a friend that signed up and she has bought some stuff through them, but I don't think she has made her $6000 back in savings yet.
Definitely don't think you would save that much on bikes. Bikes only have a 30-35% mark up in the first place. Shops make most of their money off repairs and accessories.