Those things are just so horribly expensive anyway.
So the wizard casts a maximized meteor swarm.
There are a lot of other things I'd rather spend my money on, as a 20th level wizard.
340,000 gp will get you:
28 Vibrant Purple Ioun Stones...(28*6 spell levels = 168 spell levels, max level 6th) (Might I suggest 26 of these and goggles of x-ray vision, so you can see where you are going?)
or
3 rings of Wizardry IV, (You need a hand of glory to wear them, but the 40,000 gp you have left more than covers that expense) You now cast 20+ 4th level spells.
or
Tome of Clear Thought, and a Manual of Bobily Health +5 inherent bonus to Int and Con, and a +6 headband of intellect, with 29,000 gp left over!! (adds a +11 to base spellcasting stat, so assuming base 16, +4 levels, you have gained1 1st, 2 2nd, 1 3rd, 1 4th, 1 5th, 2 6th, 1 7th, 1 8th, and 1 9th level spells extra.