Might not be so expensive:

drop bars: $10-50 depending on what you want
Tektro v-brake levers: $20
barend shifters: $30-50
brake cables: $10
bar tape: $10

You might also need new shift cables, and maybe new brake or shift housing.

Prices depend on whether you are OK with used parts.

My flat --> drop conversion cost me $20 for v-brake levers, $35 for old SunTour Command shifters, and brake cables and housing, and bar tape. I already had the bars and the brake housing, so it was under $100. Depending on your top tube length and the length of your stem, you may need to change the stem. I had to get a shorter stem. Oh, that was another $35. OK, that comes out to a bit more than $100, I guess.