does anyone ever tell the dealers of their varieties that are labelled as common stamps?
I realize I may be very different from most collectors, as many collectors are always hoping to get the great "find".
If the price difference is significant (i.e., 10x or more), I always tell the dealer. I treat my dealers the same way I expect to be treated. If they tell me they don't want to know, then I say OK and never mention another find to them again. But most dealers are very appreciative of buyer honesty.
Technically, one can argue that since the dealer didn't factor in the premium when purchasing the item, why should a I bother to let the dealer know.
I've discovered over the years that being honest with your dealers gives you far greater benefits in the long run, far more than just the couple of stamps that you happened to get a great deal on. But most importantly, I feel that not only can others trust me, but I can trust myself. This is simply my personal opinion toward myself, and is in no way representative of how I view others; so please do not take any offense.
In fact, I just informed one of my dealers today that he had a special perf variety in a few of his listing, partly because I wanted to confirm the pictures were accurate and not just a stock photo. If he doesn't withdraw the listings, then I will go buy them all. Over the years, he gives me free shipping as well as 3 months to accumulate purchases (actually, he's willing to give me even more time, I chose 3 months for my sake), and he doesn't even bother to send me any invoice.
Here on SCF, when I notice someone has misIDed a stamp that is actually much more valuable, or didn't realize there was a significant price increase in the catalogs, I will also let them know. After all, we're family, right?