Feasts are expensive, but are still cheaper than everyone bringing their own food. The reason they're expensive is that they all require an ingredient that can only be bought with an Ironpaw Token, the 100 Year Soy Sauce. Ironpaw Tokens are a non-tradable currency obtained by doing quests (including dailies, or a weekly if you're a scribe), and their short supply can be a real limiting factor on leveling cooking. Leveling the "ways" of cooking requires a lot of tokens, and once they're leveled, using them requires a lot more. If you rely on dailies for these, you'll never have enough.
A better way
Luckily for us, you don't have to rely on dailies! The first thing I noticed when I was first exploring Halfhill was that Nam Ironpaw, the token vendor, had a repeatable quest called Replenishing the Pantry that asked for a Bundle of Groceries. Once I worked my way past the Preserving Freshness quest, he did, at least. Anyways, essentially, you can buy an empty container from Merchant Cheng (next to the seed vendor) which can be right clicked on to consume some quantity of cooking materials to make a Bundle of Groceries. This can be turned into an Ironpaw Token.