How much, asks Tobold, do you owe a pickup group? He uses the example of Seaforium charges on locked chests-- they can "cost" up to 5g in mats, so is that too much for the engineer to contribute to a group of people he basically doesn't know? Potions are the other big question, but I'd expand it to include everything you bring to a pickup group: just how many times do you need to wipe in a pickup group before you're free to ditch them and move on?
I happen to be pretty much like Tobold. I'm not rich in the game or anything, but the money doesn't mean much to me (this is, after all, a videogame), so I'm more than willing to pass out potions at bosses, or stick with a PUG until my gear is red. I guess there are some things I wouldn't spend on a pickup group-- repair bots are just too expensive to use among people you don't know, and while I'm often willing to give lower level enchants away, the higher level enchants I usually save until there's a guildie around that I know can and will use it.
Tobold says, rightly, that groups are "worth" much less in WoW than earlier MMOs-- because you literally can solo all the way to 70, a lot of bad groups can be avoided, whereas in older games, you had to suffer through a lot of bad groups just to level, because there was no other way. But of course it is still just a game-- a good social experience is worth way more than a potion or two, and you never know if the Warrior you give an Onslaught Elixir to today might end up being your main tank tomorrow.