What's the best thing to cook at my level (80). I know wines are good exp, but I'm hoping for something a little more AFK, and less than 4 gp/xp. A progression as I go up to level 92 would be fantastic as well.

Sharks/monks/swordies don't cost much, use cooking gaunts if you have them.

 

This is a handy tool...

 

http://runescape.wikia.com/wiki/Calculators/Cooking_fish

With gaunts, lobs to 81, swords to 90, monks to 94, sharks to 95, rocks to 99

Excellent, thanks to both of you

With gaunts, lobs to 81, swords to 90, monks to 94, sharks to 95, rocks to 99

 

This is the path I took (minus the rocks, as they weren't out yet, so it was sharks to 99, but essentially all the same). If you have the Varrock Armor 3, you can use the Cook's Guild, or Rogue's Den under Burthrope. Those are really the only two places to cook I'd recommend.

Adding urns in your inventory makes it cheaper as you gain a little bonus xp.

It takes 2 inventories of monkfish to fill one, so you'd need quite a few for 99.

I just got 99 on the weekend. Here's how I did it:

 

-Use decorated cooking urns (cheap and a lot of extra xp means money saved)

-Use Cook's Guild if you can, otherwise Rogues Den or (where I went) Nardah. I prefer Nardah because it's more secluded and the bank never moves. Plus you know when people are botting goats and you can report them.

-Lobsters to 81, Swordies to 90, Monks to 92-94 (at 94 sharks don't burn, but faster xp if you start sooner and you burn very few), Sharks from 92-95 depending on where you started using them, and Rocktails to 99. I highly advise not using Rocktails till 95 because the loss from burning can be big over time.

 

Of course, this assumes that you have Cooking Gauntlets which you should have anyway. Quest is easy and short, and the rewards are great (Cook Gaunts and Gold Gaunts)

If you're leveling for effigies you only need 91(2?) to do them all with mature chefs delight. What others have outlined for fish is fine, I would recommend looking at wines though. The time saved by training at over 400 k exp/hr can be used to more than make up for the loss of money.