This is why I am actually relieved when I hook a fish, and it manages to escape the hook without me handling it...while I enjoy getting it close enough to see, I often release line tension to aid its escape. On those few occasions when a fish takes my barbless fly (and I don't fish any barbed hooks) too deep to rapidly extract the fly, I have no problem nipping off the tippet. IMHO the value of an unharmed fish is far greater than the negligible cost of a fly I tied myself. Of course, this is easy for me, since I never eat the damn things anyway. For me, it's the challenge of getting the fish to strike via the right presentation (which is a shitload more than just a good cast and the right fly) and to react fast enough to set the hook. It's especially satisfying when the fish's take of the fly (especially wetflies) is very subtle and easy to miss. Anybody can set the hook on fish hitting aggressively on dryflies.