For balance reasons, alchemy is severely nerfed.
To pick a single example, consider the 4E version of the Smokestick (which you'll find in Adventurer's Vault).
It's a stick you can throw that when activated creates smoke.
In a burst 1 area (i.e. nine squares). This won't even fill a small room.
You can throw it a maximum of five squares. (That's right. Theoretically, you "consume" the stick and the effect happens up to five squares away)
The smoke isn't stronger than everything inside is lightly obscured only. And it lasts two turns only (about 12 seconds)...
Okay, so what does this baby cost then? 150 gp (plus the standard "sales tax" of up to 40%)
And what does its recipe cost you? 450 gp, and you can't create any unless you're at least sixth level and have the Alchemy feat.
And that's a puny Smokestick only! I can't even begin to imagine what epic requirements there would be for actual gunpowder...