This is a hard question to answer because I don't know the volume a dealer buys with but:
Is there an average % the dealer makes on an outboard ?
Dunno
I was told the postitive aspects of a higher gear ratio 2.5/1 meaning 2.5 prop turns for every turn the motor makes.
That would be 2.5 revolutions of the engine before your prop completes one (otherwise your prop would be doing 15000 RPMS at 6K on the engine. This allows a a longer "screw" in propping, better holeshot...
What are the down sides to a gear ratio of 2.5/1 ?
Potential loss of top speed but many other factors influence that
Are there any "hidden costs" when repowering that caught any of you off guard?
dunno
I few things I learned at the boat show,
Suzuki and Johnson 4strokes are the same motor, Suzuki.
Yamaha 4strokes go from 115hp right to 200hp none inbetween.
All dealers say "I'm going to be honest with you".
"I have a car for you - driven by an Old Lady only on sundays to church 
".
I think $12 to park in a lake is a bit expensive.
Huh?