My pack doesn't do it, but a neighboring pack holds PWD workshops where this is the only place to make the derby cars. Both parent and Cub have to attend, and the work is done by Cub Scouts, with parental assistance. Power tools and other hazardous tools are strictly done by an adult. The derby cars for that pack, never go home!
The thought of spending $100 for a $5 hunk of wood is ridiculous! Maybe you want to take that parent aside and say "hey man, I heard from chit chat in the pack that you spent $100 to purchase your car. I'm not going to judge you, but if it is true, think of what you lost because your son will never say, my car won because of what my dad and I did together."