I think the plugs they put in are iridium or something like that. Don't ant to state the name of the shop at this point. I'll talk to them and see what the respons is. Maybe just a typo or something weird.
I'm not familier with the price of outboard repair but.......Are you sure that $20 ea. is Only the part price or did they ball the part and labor price together for each plug?
FWIW.......Being an auto mechanic, I have paid $12. apiece for plugs for certain cars......If I worked at a shop like Goodyear, Mr Tire, ect (which I dont, but have) and plugged $12 into there standard mark-up schedual, those $12 dollar plugs would cost roughly $20-$24ea.
Just for the record, I work for myself and put minimal mark-up on parts.
Plugs for my 135 Opti were $15 a piece. Had not been changed in two years so I bought a set a few weeks ago. Started pulling them and they all looked great. Checked the gap and put the old ones back in and took $100 worth of plugs back.
I recall my friend had a Evinrude 225 and had the same complaint about cost of plugs... I looked up that part number above (fits Honda 225) and it looked like it retailed for around 15...Discounted on the Internet for around 12.... The price sux, but it might not be the total fault of the mechanic if 12 were installed.