Is my local bike shop asking to much money to change a rear cog? I normally have much love for my LBS, but I've moved recently and am a little unsure about this new one due to the fees he is asking.

I have a flip flop hub with a fixed gear (18 tooth) cog on one side, and a freewheel single speed cog on the other side. I need the fixed gear cog replaced. As I understand all you need to take this off is a special tool every bike shop would have. I assume the whole replacement process would take all of 5 minutes - quicker (like 2 min) for an experienced mechanic -- is this true?

The shop wants $50 labour to do this. Seems a little steep, I think! Am I right to think that this rate is unreasonably high?
Ah the internet.

Answered my own Q:

It takes about a minute. Yay!

Watch at 2:13: Replace Fixed Cog (broken link)

Instead, try


How To Change A Track Bike Or Fixie Sprocket  (splined).
FIXIE COG INSTALL #3 (threaded)


For DIY: need a chainwhip and a lockring wrench / lockring spanner 

...or a multi-tool with chainwhip &amp; lockring wrench!

Done.