Is it Cheaper to Tie Your Own Flies or Buy Them?
It can be cheaper to tie your own flies if you fish a lot (i.e., go through a lot of flies) and if you stick to tying a small number of patterns that require limited materials. Sticking with a $20 vise, a few tools, and thread, yarn, feathers, and hooks will save you money in the long run. You can catch fish for the rest of your life on just a few patterns tied with these items and be perfectly happy.
The problem comes when you get really into fly tying and start getting interested in tying a wider variety of patterns and colors. Fly tying becomes a hobby in and of itself for many people. Buying materials will probably end up costing you more than just buying the flies outright from an inexpensive fly shop.
For many people, tying flies starts off as a money-saving endeavor but then morphs into a full-fledged passion. That's OK too! In the grand scheme of things, fly tying is still a relatively inexpensive hobby.