Certainly anything can go too far, but the general notion of magic for sale to me does not cheapen it.
Does having a longsword for sale spoil them?
Does having a suit of plate mail for sale spoil the mystery of armor?
Not hardly.
In "standard 3e" its pretty much expected that HALF your party will be spellcasters, typical "standard" of a mage and a cleric.
MAGIC has no luster, mo mystery, no "rarity to be cheapened if thats true.
Assuming no epic levels, just the normal 20 levels...
By the time you are a neophyte at say 5th or sixth level, about 25% down your way, you have people in your party who can routinely....
Heal wounds, cure diseases, paralyze people, enchant weapons to +2 and summon elemntals all on the spur of the moment... thats the cleric...
throw booming fireball, lightning bolts, turn people into mist, fly, become immune to normal arrows, walk on walls and ceilings, go invisible, etc etc etc... those are the mages...
by 9th level at a whim you now can RAISE THE DEAD and toss out 9 hour long +3 enchantments at the drop of a hat, much less teleport, stone walls, scry, etc...
The "mystery" of magic, that which is cheapened by having items sold, does not exist when its commonplace for you and your friends to do it.
The "ohhh ahhh magic item thing" does not compute when the item is something you can do yourself at a whim.
The "ohhh ahhh" of myth and legend... lets see who was it who got the helm of invisibility and sandals of flying in greek myths from the gods.... and a reflecting mirror... are not all of those parlor tricks to a 5th level mage?
Hey wanna eliminate spellcasters and then run a "magic items are mysterious and wondrous" and it will work... but frankly no matter how much salad dressing you put on it, for a mid level group a +3 sword isn't that important... they can spell their own at the drop of a hat.