As many prior posters have mentioned initially it is quite expensive to tie your own flies versus buying them from an on-line, off shore, source. BTW there are two off shore makers that I am aware of that tie great looking flies in all sorts of sizes and styles. I rarely buy a fly but I have noticed most of those flies have no head cement an they often unravel quickly. So if you buy on-line you might want to put a tiny drop of head cement on the fly.
Because it costs quite a bit of money to buy a good vises, half a dozen thread bobbins (at least) two pairs of scissors, other tools, hooks, hackles, fur and hair on the skin, premixed dubbings, thread, wire, tinsel, chenille, various strung feathers, wood duck, etc. it will be quite costly but once you have a good assortment of materials to tie nymphs, dries, and streamers for the waters that you fish it is less costly especially as your speed increases.
Obviously as others have also said if you don't really like to tie and are doing it because you think you can save some money you should just buy the flies and either go fishing, or take your wife out, for the time you aren't tying.
On the other hand if you enjoy tying and realize that there are all sorts of trout flies that you just can hardly ever find in a fly shop like figure 8 hackle wing spinners, really good thorax flies, hackle stackers, hatch specific nymphs, the list goes on and on. I love to tie and have been tying for sixty years. I probably tie over a 100 days a year. I just finished two dozen #14 Hendrickson nymphs for next year and two dozen #18 PMD nymphs for my annual Montana trip.
Fly tying is a great hobby to enjoy anytime but especially after the normal season is over if you don't steelhead fish. I have over forty fly boxes and the last time I counted over 10,000 flies.
All the boxes wouldn't fit in the viewfinder!