I think around 40-50 dollars is about average.Sounds like the Taxi you went to charges about $464.16 per hour.If it took 20 min to put crate together.
I know the wood at Lowes, for 4'x1"x4" is $1.56 ea. So the wood would cost $20.28 and 154.72 x 3 = $464.16/Hr.
It is best to find out all of the charges and any hidden charges in advance and have them included on your bill of sale so there isn't any confusion.
Also it is good to do your research on taxidermists just like you do on a guide so you don't end up with a hacksidermist.
Elkshed