A hair transplant is also an option and relatively affordable nowadays (I paid 1600$ for mine, in Turkey). I was initially skeptical and had very low expectations but in the end, I'm very happy with the result. Normally, you don't lose the transplanted hairs because they are taken from the region of your head that doesn't go bald.
Here's a pic of me shortly before (left) and a few months after (right): https://raw.githubusercontent.com/olalonde/olalonde.github.c...
Edit: Thanks for the compliments :) To answer a few questions:
I was already visiting Turkey for a friend's wedding at the time so I didn't need to get a complete package with accommodation, etc. In fact, I decided to do the transplant on a whim, partly because my friend wouldn't stop bugging me about it (I'm glad he did in retrospect). I decided to do it, went for a consultation the following day, and had the operation the day after that.
I don't know what truth there is to this but I supposedly got a good deal because I didn't need transport, accommodation, etc. They politely asked me to keep the price to myself, so I feel ambivalent about posting the clinic here but I'll happily reply to emails (see profile).