Some elements I agree with:
DragonSword said:Magic items can't be bought easily. A player can't just remove 5,000 gp from his character sheet and get a really cool magic weapon.
pdkoning said:In a low-magic campaign, players have to use more 'real life' solutions than magic.
Jürgen Hubert said:All in all, I'd define "Low Magic" as "powerful effects are rare" and "the price to cast magic is too high to use it casually".
Turanil said:For me, D&D 3e tends to be a game of 20th century consumerist society with a medieval perfume.
Zappo said:For me, low magic is when the presence of magic has no noticeable effect on the society as a whole.