10 keys is a small sample space, so obviously you can't divulge very much, but at least it is sampled.
========================
10 keys bought for 6 platinum
========================
============
1st drop:
============
============
2nd drop:
============
============
3rd drop:
============
============
4th drop:
============
============
5th drop:
============
============
6th drop:
============
============
7th drop:
============
============
8th drop:
============
============
9th drop:
============
============
10th drop:
============
Statistics:
PURPLE: 6 (60% of the time)
GOLD:4 (40% of the time)
CLASS:# of drops:total value
W: 2 (20%): 336g
Mo:3 (30%): 656g
N: 1 (10%): 152g
R: 1 (10%): 392g
Me:1 (10%): 174g
E: 2 (20%): 604g
1: purple-warrior-142g
2: purple-monk-110g
3: gold-elementalist-312g
4: purple-necromancer-152g
5: purple-monk-186g
6: gold-ranger-392g
7: purple-warrior-194g
8: purple-mesmer-174g
9: gold-elementalist-292g
10: gold-monk-360g
Total value: 2314g out of 6000g (38.56%)
Net (Loss): -3686g (61.43%)
Note: I ran wildy around Ember Light Camp looking for the chests in no ordered manner. Assume that location of each chest has no bearing on the value of the drop. Mainly, there is a belief that the farther or harder-to-access chests drop better value items, but I cannot conclude anything about that. Also note the total value of all the items if sold to the merchant, which is 2314g. The total value of the keys themselves is 3000g (if sold back to the merchant). These all seemed to consist of so-so mods, although all weapons/items are max damage/energy. This also brings up another point, and that is the introduction of new professions. For those that only play 1 or 2 professions, finding an item of your profession is going to be increasingly harder. Add the two new professions in Factions and your percentage is going to drop even more.
If I had gotten one good drop out of these 10, then the results would look more positive. Still keeping in mind this is only 10 runs, the general look of the drops do not look impressive. I am thinking of attempting to salvage some of the mods, such as the zealous or enchantment mods. I hope someone else decides to do their own run and test, so more samples can be added, but my personal take is that I will never buy another key again. Anyway, if anyone has any questions or sees an error or if this is in the wrong forum even, ask away.
-[XGZ]
X

, change a variable and make it 20 keys.
most of the time, chests are crap
)