Its official... Alchemy at a high level is epic. Single best way to make money in the game. I started buying up everything useful from any herbalists in holds I visited, plus the stuff I found when adventuring. So I went on a potion-making spree tonight, focusing on the most valuable potions first. Not only got my Alchemy up to 93 (from about 83 when I started the spree) but am making a ton off the potions sells. I've sold about 2/3 of them so far and made 15k gold. More, really, as I cleaned out almost every merchant I went to of anything I could use, so they had more gold to buy potions off me. A few of the potions are worth over 1k apiece and a lot are worth 500-750 gold. So the tough part is traveling around to merchants to sell them. Time consuming. But oh so profitable.
I'm not even really maximizing things yet, either. I buffed up some items awhile back to make more potent potions but could do a lot better now. Just haven't bothered yet.
Alchemy isn't like Smithing, where the skill increase you get for each item is the exact same regardless of item. The skill increase you get is based on the value of the potion created. So it pays to focus on the more valuable potions, every which way. You also want to use the 5 main perks to increase the potency of your potion - again, it will help you level faster. Using enchanting to buff some items provides another slight boost.