The $50 you spent is not unreasonable. Some local gunsmiths might be lower...
Novak's charged me $35 to change the sights, and sold me the new ones for $69.90. That seems reasonable. (It cost me $8 to ship the slide to them, and $14.34 in shipping and handling for them to send it back. And no tax).
See their web page Novak Designs Inc. - Main Page
for a full price schedule for various options. I feel I got good value for the money, and picked Novak's for this work because they did such a good job on my Mdl 915 (where the old sight cut had to be re-milled) and because they are a top-notch company that knows 3rd Gen S&Ws.
I bought a MGW sight pusher for my M&Ps when I went through a couple of them and did some Apexing and changed out the standard sights for Warren Tactical sights (which are great). The sight pusher cost around $120 and I reckoned it was worth owning if I changed more than two sights myself (plus it was faster). Then I sold the M&Ps and the sight pusher and recouped most of the cost. But with 3rd Gen S&Ws, I don't know how well a sight pusher would work -- and I've read some of the sights on these pistols are very, very tight and hard to adjust. Another reason why I went with Novak's.
All I can say is now the 5906's sights are a lot easier for me to see and are accurate, and I'm happy with the work.