I have assembled 5 ARF planes this summer. The last plane I assembled was a smaller version of one of my bigger ones, and the process was almost identical. It still took me like 4 full days. Normally it takes 2 weeks to build a plane when you have other things to do as well. If I gave someone 4 full days of my time plus supplied necessary materials and used my own tools I would expect more than $300 if I were doing it for a business.

I can't imagine the other hobby shop could really get your ARF plane together in a day - it was not an RTF (ready to fly) plane, was it?

I don't think your plane being flown is totally unreasonable. I probably wouldn't be too excited about it either, but from his perspective - if he's going to build your plane and charge you $300 he probably wanted to make sure it worked right and you wouldn't have any problems.

Not trying to say you are wrong or anything - $300 is a lot of money and it's exciting to start up a plane for the first time, but you hired the man to do a job maybe without knowing all the details first.

You now have a fully built and working airplane - fly it and have fun!