I have heard others say that it is the quality of the airframe and the engine that are important, not the quality of the paint.
Yeah, it's true. But take it from experience - if the plane doesn't make a good 'first impression' visually, most people walk away without really looking at the machine. I've been trying for months to sell my 150H at, I believe, a reasonable price. She's good mechanically, but in dire need of paint, radio and a rear window. Most people that have looked at her didn't even pull the cowling or look at the logs.

"It's ugly, so it must be bad."
So I guess I'll spring for paint job and increase the price to cover.