Need help with the pricing for magic items

[Meepwizard]

For a campaign I'll be starting at some point there'll be a magic item merchants guild where you can pay some amount of gold to then roll on a chart for which item gained. The problem is that I don't know how much each table should cost(I guess it really depends on how much I give out during the campaign)
Charts:
Potions
Scrolls
wands/staff
Common magic item
Rare
Etc...

If you know of any good sources for pricing please point me in that direction, if you yourself have any advice on pricing that is appreciated as well.
I do know of the sane magic items thread, but this will be based off of rolling, which is what I have trouble with thinking up.

[Bubzors]

http://www.giantitp.com/forums/showthread.php?424243-Sane-Magic-Item-Prices


That is something I have used before. Not official but pretty good judge for how things should generally cost

[Balain]

I never likedthe ideaof all +1 weapons are always 1000 gold.

I don’t have my book here to check pagenumber, but somewhere in DMG before the list of items there are some tables for trying to find a buyer for a magical item a player maybe seling. I have usedthe same tables for pplayers trying to buy items.

the merchant may have common items like potions but any magical item like a weapon will take him some time to find or make. If you end up with a low price, well the item isstolen or some such thing and if the players take the offer will now there is a nice possible side quest or another hero out looking to find his stolen item, and he eventtually finds the vile player that took it.

[Azgeroth]

if you can (and i dont have time to do it right now, maybe later?) it makes the most sense to price magical items on the trade of wizards and their schools...

for example, wands will be on sale specifically to generate money, though some will be 'restricted' (not selling a wand of fireball to just anybody now are they?)
bags of holding, handy haversacks, potions, scrolls, the occasional weapon/armor (made to order, never collected, retrieved in an excavation etc.)

everything else would be priced according to demand, and usefulness.. example, i don't image any wizarding shop selling a rod of absorption, but they might, if they have something in place that is better.

something i think is quite lacking at the moment is stationary magic items/equipment.. magic items are portable, what if you didnt need to carry it? what if it just stayed in one place..

though that is a pretty high magic concept, it should still help decide how to price these things..