Cutting these gems loses this
gp/xp - xp per gem - gp/gem
Sapphire - 27.66 - 50 - 1383
Emerald - 33.88 - 67.5 - 2286.9
Ruby - 39.21 - 85 - 3332.85
Diamond - 47.95 - 107.5 - 5154.625
Dragonstone - 47.85 - 137.5 - 6579.325
Then because you need to cut x amount this is the total loss for 5m xp using all these gems.
Sapphire - 100,000 = Loss 138.3M
Emerald - 74,075 = 169.4M
Ruby - 58,824 = 196.05M
Diamond - 46,512 = 239.75M
Dragonstone - 36,364 = 239.25M
Each one of those prices needs to be multiplied by 2.6 times for 13m XP, which is approximately 99.
Sapphire - 359.6M
Emerald - 440.5M
Ruby - 509.7M
Diamond - 623.4M
Dragonstone - 622M
(Onyx isn't realistic for doing, hence not included)
So no, for 250M you can't cut gems for 99, you need atleast 360M.