If you're willing to break the strict numbers economy of 4e, maybe take a cue from Warhammer 40k Rogue Trader. In it, you've got so much money that you don't buy a grenade. You buy "access to grenades forever." Thereafter, you have as many grenades as you'd ever need, limited by how many you can carry.
HP scales a lot, defenses scale even more, which make low-level alchemical items useless at high level. But if you make alchemist fire a "weapon," ranged thrown, with 1[w] equaling 1d6 fire, plus ongoing 5 fire, then you could charge a price of 10gp for normal alchemist fire, 500 gp for a +1 alchemist fire, etc. And then you get up to 10 uses per day.