I think it's eminently clear that Alchemist's fire in particular, and possibly also other alchemical items, can't be made with Fabricate.
The "a product" line is news to me, and I'm not sure if it's meant to be interpreted that way, since presumably you could make a deck of cards, chess game, or quiverful of arrows with Fabricate without anyone batting an eye.
Personally I've never seen anyone use Fabricate for anything in a game, but if a player tries this scheme, as far as I'm concerned you have four options:
1. You can ban the spell outright if you don't want to deal with it.
2. You can write a revised Fabricate spell that doesn't break the wealth system (Probably tricky, unlike Polymorph and all those I've never seen anyone try)
In either case you should allow a PC who's learned Fabricate to exchange it for another spell.
3. You can say someone has tried this before, and that there are laws, guilds etc. in place which prohibit it on pain of dire punishment. In this case, the PC should most likely know that beforehand (although depending on the character, he might not.) In this case I would also allow the PC to learn another spell in place of fabricate, since I created these laws after the fact.
4. You can let him be the first. This will soon lead to great anger from various mercantile interests, various economic cataclysms, copycatting etc. but, and importantly, most likely not before he's amassed a vast profit, if we are to be at all realistic about it. Assuming he has the wit not to restrict himself to a spesific good, there's always someone who needs a bunch of weapons, or uniforms, or whatnot. Once you get over the notion that it's "wrong" for him to have all this money, this is actually a very interesting scenario.
After all, what's he going to do with the money? As Fabrication becomes the new industry standard, the prices of most goods will drastically fall, so this won't actually be a means to vast wealth for very long. Eventually it will become the only way to be competitive. Hope he's invested his money wisely. But ah, speaking of falling, so will the status significance of eg. beautiful statues, luxury furniture and other things which just about anyone can have Fabricated for them. If he spends it all on magic items, good for him, but:
1. Other mages elsewhere will probably do the same, so he might find himself with a lot of emptied mage-shops and well-equipped adversaries down the line
2. particularly quick copycats might even end up competing with him for items, and with so much gold on both parties' hands, the bids can get quite high...
and 3. Relatively weak people with cartloads of magic attract lots of attention. That applies to money, too, for that matter, but even swarms of thieves isn't as bad as treasure-greedy dragons and evil adventurers.
Whether or not he manages to survive all the people who are now out to get him (many, many adventure opportunities here), you are left with a world full of wizards who have discovered the wonders of Fabricate. Old guild leaders will be pushing for laws like those in 3. above, but most likely, rulers will see this new method of wealth production as too tempting to prohibit. More troublesome to them is the fact that if you can fabricate a wood medallion from a log, you can fabricate coins from gold or silver! Those countries with the largest number of Fabricate-willing mages gain a vast economic advantage, which shifts the balance of power in the world. And you get a pretty cool campaign, I'd bet.