Money is for housing mostly, it seems. I'm thinking every major city has a house available, and that adds up to a lot.
Housing is the only thing I've encountered that costs more than 5k. I don't think I've seen a magic item worth that much even. Grand soul gems with a grand soul? 1500ish. Everything seems priced fairly low in Skyrim, it's just the bulk purchases like spells that end up costing you a lot. Or materials I suppose if you're not doing a ton of wandering or stealing and want to get straight to the cool smithing.
Alchemy is more or less what it was in Oblivion. Each reagent has 4 properties, using reagents with the matching properties yields the potion. You can combine up to three items, and I haven't tried for potions with multiple effects yet. You can eat ingredients raw to learn their properties, or mix and match them on the alchemy menu, and it will grey out combinations that don't work. Unlike other alchemy systems, you don't create potions with "failed" combinations, it just doesn't work. Alchemy is really useful.....but not terribly interesting IMO. Like enchanting, Bethesda purposefully gimps how expansive the system can be. The Alchemy perks do allow you later on to craft potions more to your liking, by having remove the "poison" effects from combinations if a good effect would come out of it. But that's pretty much the extent of it. The effectiveness of potions is based on your skill level and whatever perks MASSIVELY augment their power.