I recently took up cooking and if you get serious, it gets expensive, specifically in the following ways:
1) Stocking up - Initially buying spices ($4 each), pots, pans, trays (a decent set will run you $400), a good knife($80) which you will eventually need, other staples ($a bunch)
2) Experimenting - You'll get stuff wrong a lot. You'll ruin food. You'll buy more food. Sometimes it's expensive food like steak.
3) Showing Off - When you figure out you can cook something that is noticeably better than rubber, you'll want to cook for your friends. They will like the food and thank you, but they won't always remember to leave cash behind.
4) No more junk food - Cooking the good stuff makes you appreciate good food, and by appreciate I mean spend more money on.
I find cooking to be a lot like programming. There are tons of options and methodologies and evangelists and opinions, but when it comes down it, the thrill of creating something (even something palatable only to you) is unbeatable.