Where do I buy good quality (for truffles) chocolate in bulk quantities (> 3 lbs)? The prices I'm seeing for Valrhona, etc on Amazon reach nearly $15/lb and that is ridiculous. Any preferred vendors? Thanks!
In the world of high-end chocolate, Valrhona isn't even the most expensive - in fact, it's practically entry level. Amedei Signature retails at a whopping $40/lb in "bulk" (1 kg) quantities.
I don't think I've ever seen Valhrona in bulk quantities and/or at a significantly discounted price. On the other hand, there are similar-quality brands that are way more affordably-priced. On chocosphere you can buy 22 lbs of Callebaut callets for just over $6 per pound. Or you can get one of Felchlin's Grand Cru chocolates for about $10 per pound. You can even buy Guittard there for what appears to be $6.60/lb. But you'll notice that they even though they also carry Valrhona, they don't have it in bulk.
I also see Candy Warehouse selling the Guittard wafers for, apparently, $3.10/lb if you buy the 25 lb bag. Chocolate Man sells the Felchlin Maracaibo chocolate (not Grand Cru) for a measly $7.80/lb. They've got a variety of other well-known brands as well, although their selection is limited, they don't have a lot of the crazy high-end stuff.
Chocovic chocolate also sells at around the $10 range at most stores. If you can find it, they distribute 10 kg and 25 kg bags (that's 22 lbs and 55 lbs). I'm not sure where, but if you go to their official site they explicitly mention that they make that size.
You should consider that the exorbitant prices may not be a result of where you're buying from, but of what you're buying. Valrhona is just expensive. You may say that is because it's better than all the others, and you may be right (although some would disagree - it's more than a little subjective) - but that is the price you pay for "premium" products. They can get away with charging $13-$15/lb, so they do.
Do yourself a favour - try some of the lesser-known brands. A lot of them really do make fantastic chocolate, they're just not as famous as Valrhona.
Chocosphere has been my source for around a year or so:
They are based on Oregon (unfortunately for me), but they sell all of the most common brands of chocolate. Most of their chocolates are sold in 1 kg, 3 kg, or 5kg quantities. As a bonus, they are really good at shipping. I've had them ship chocolate literally across the country in warm weather and it showed up unmelted.
EDIT: As others have noted, Valrhona is NEVER cheap. Ever. And Valrhona isn't the only one. I've been wanting to try some Michel Cluizel stuff, but its $40/kg!!! I use cheaper chocolate, such as Callebaut, when I'm working on recipes. When I'm making anything that's going to be boxed up, I may order different chocolate. A current (and rather unknown) favorite, is Chocolate Santander, a Columbian single-origin chocolate that beat out all the Valrhona varieties I had on hand (2 or 3), Callebaut, and about 5 other chocolates I had around in a taste test.
Try Guittard products. I think they stand up well against Valrhona. I use Scharffen Berger cocoa and I buy it in bulk.
I have used Chocosphere in the past - good customer service, but their prices are not as competitive as they used to be. I've been shopping around on the web and can sometimes beat their prices by enough dollars that I try new places.
For truffles, I use the Guittard 63 (it might be 62 percent) dark chocolate 10 pound bar. Worked wonderfully and overall cost for the chocolate on a per pound basis was very good.
I'd have loved to try the Divine Chocolates site listed in this other answer but "contact us for price" is a nonstarter. I want to be able to compare prices online without waiting on office hours or having to speak to someone.