It's normal to have many low magic objects and few powerful one.
Yes, that
would be normal. But I ran the generator at least 50 times and the pattern I was seeing was that roughly 1/10
challenging encounters at the
highest magic level maybe had a powerful item and usually that powerful item was a one-off consumable, like an expensive scroll. 9/10 of those encounters dropped low level potions and scrolls and a small pile of mundane gear that doesn't even matter. This was consistent throughout levels 3-15 (I didn't test higher or lower than that).
But maybe I'm misunderstanding the purpose of this generator. If it's not supposed to generate a party's Expected Wealth by Level, then this is probably not a problem.
EDIT: I found that if I adjust the settings to Epic difficulty, Fast pace, Triple treasure, Standard magic level, and 34% residual value, I arrive near enough at expected party Wealth by Level guidelines (a little higher than normal, but I'd assign a figure close to 10% that appears to be treasure of such negligible value comparative to character level that players would probably leave it where it lies). Again, this would seem to be a problem, but only if this generator is meant to generate the party's Expected Wealth by Level. If it's not meant to do that, then it's not an issue.
The higher the gp balance value and the higher the magic level the more you'll have a chance to obtain a powerful item.
I'm not seeing any "GP balance value" anywhere. If users could tweak the GP balance value of the simulated encounter that would probably help.
EDIT: Another thing I noticed was that the value in coins is severely messed up. I don't know how the conversion could even get this screwed up but 1 Platinum = 10 Gold, 1 Gold = 10 Silver, and 1 Silver = 10 Copper. Right now, it's telling me that 881 PP = 881
7.9 GP and that 3399 GP =
3391.5 GP. What??