Hmm, I thought XP for treasure went out with 1E? I don't remember using XP for treasure in 2E.
It was there as an optional rule. Unfortunately, its removal completely broke the the XP system.
In AD&D, characters gained about 20% of their XP from killing monsters, and 80% from getting treasure. In 2E, according to the guidelines as written, they'd get 50% of their XP from monsters and 50% from story awards, with no adjustment upwards for the XP from monsters. Thus, levelling was at 40% of AD&D standard. (Which was approximately once every 5-8 sessions for levels 1-9).
This is unless you were a thief, who amongst their individual class awards gained 2 XP per gold piece value of treasure obtained. No mention of using their thief abilities to gain it. Yes, a lot of people *included* that, but given that XP for treasure wasn't included for everyone else, it caused a mockery of the XP system with thieves going up much, much quicker than everyone else.
It should be noted that Gary Gygax may well have used the Individual Class Awards that were presented in 2e; he made reference to similar awards at one point in AD&D and was surprised when we told him that they weren't in the rulebook...
There are several major flaws with the 2E system, but the top of my list has always been its XP system.
Cheers!