As others have mentioned, the commissions and fees really kill someone's incentive to have one of these, as well as the delay when you first get started with setting one up while you wait to find out if you successfully bid on a spot (while 80% of the surrounding spots are empty and have always been empty). Also, some people may be under the mistaken impression you have to upgrade with one of the theme packs to actually buy from a bazaar vendor. You only need to upgrade to run one of the vendors.
I have two pet vendor stalls on Siege. One sells pets that don't require taming and the other one currently sells battle chicken lizards (if it isn't empty by now, which is highly doubtful). At this point, any profit I could have made off the critters is ancient lost history, long ago eaten up by fees. I just leave the stalls up as a convenience for the reds and newcomers and the rare person who wants a colorful battle chicken lizard with so-so stats. One of these days maybe I'll get industrious again and put some golems on one or the other of them.
A few other folks have pet stalls on Siege and there are also some selling AND buying commodities. If you're curious how the one that sells and buys imbuing resources is doing, just log on Siege and ask for the person that runs the Sam's Club vendor to chat with you a bit. He's on almost every day and he probably wouldn't mind giving you some pointers. And if you want to go take a look at them, make a character on Siege (don't pick a paladin though or you'll end up stranded on Occlo) and use the moongate system to go to New Magincia. (If you start out in Britain, there's an out-going moongate north of the west bank, by the tinker shop.) I haven't seen a red yet that lurks by that gate, so you should be able to skip right over the grass and through the sheep and into the New Magincia guard zone with little or no danger. Then have a look at the many shops and bazaar vendors in New Magincia. Or go to the "hub" house Kelmo has set up directly east of Umbra and use the teleporter tile for the Siege Community Mall (Vlad's vendor house in New Magincia) or use the crystal portal and say "Fel Magincia Mint" to go to the New Magincia bank. The hub house is just outside the guard zone so you'll have to be a tad bit cautious there.