We did a lot of customer development work (and were customers ourselves) to validate these issues. The problem was keeping people on the site - they reverted to email and phone once the novelty of doing it online had worn off.
Wine Connoisseurs don't WANT TO BUY LESS EXPENSIVE WINE. They don't even want to buy fine wine vintages for cheap prices. To do so would cheapen the fashion that is fine wine purchasing. Sure, they'd like to be able to say they got a "good deal" from a reputable distributor, but that only goes so far.
It would be like buying your Prada products at Walmart. If Prada were to sell through Walmart, it would destroy the brand and the appeal for the people looking to purchase it.