In one way it sounds a good price to get something done well, on the other hand it sounds expensive just to bolt a bit of metal to a frame and stick a chain through it.
In answer to a comment above, “all you need are” wire cutters, allen keys, screwdrivers, chain tool………… if you haven’t done it before then consider the cost of purchasing these versus handing it over to an expert.
I think people fail to consider the fact that everyones brain is wired differently and where one person see’s first time the direction that chain runs through the mech, there will be others, like me, who stare at it for a long time waiting for inspiration. I can do the job, don’t get me wrong, but i have friends who can do it in 5 mins versus my 30 mins to an hour.
I am also unable to accept anything other than perfection with regards to set up, that coupled with being a mechanical div, generally means asking for help!
I will sign off on a positive note and say that there is a feeling of immense satisfaction when you do it right yourself!