[larsdangly]

The point is that if your XP gains follow RAW (you pay based on your stat total at that moment) then a character with a disadvantage begins closer to the 40-stat-point 'wall' than a character without a disadvantage, and they effectively skip those first few points that are very cheap. The only way the disadvantaged character stays ahead of the pack is if you don't count their initial stat point bonus when you calculate XP requirements for advancement.

However you think this should work, one great thing about hcobb's suggestion is that it just takes the whole problem off the table. You get a flat pay-out, worth 500 xp per point of disadvantage, and that's the end of it. What I like about this is that packages disadvantages as sort of like 'anti-talents'. Which is not so different from their role in the game.