We pretty much built all of the seat parts ourselves. You'll see that if you gain access to the pictures in my thread. We took every piece of the existing interior apart looking for things that could be used as templates.
We build the seat bases and structures. Then they were coated with epoxy resin, and then either upholstered or wrapped in carpet. yes, the wood structure is heavier than what was in the boat, but it was negligible.
I got 3 estimates for my boat interior and they were widely different:
1. The most expensive was $8,000 for a turn key, drop the boat off, pick it back up kind of deal.
2. Another was $2500 to redo the existing seats + undetermined more for the open bow that I/we had nothing salvageable from.
3. The guy I ended up using works out of his workshop in his back yard. He is a retired furniture maker. He had done boats before. His work is NOT perfect. My boat doesn't have a Viper Customs type of interior. But I paid $1,000 to him for his labor. I probably had $300 in vinyl and $250 in my captains chair. The rest was my own labor (and that of my uncle and cousin.)
I like the way it turned out for the price I paid. And I don't mind my kids crawling all over my $1500 interior all day and eating chips and drinking soft drinks on it, etc. If I had 8 grand in it, that'd be a different story.
Some of my foam was reusable, like the back bench seat base foam. Other foam had to be redone. I didn't have a specific foam expense though. My upholstery guy supplemented what he needed from his personal supply and built that into my cost.
here's where I ordered my seat from. Once I picked out my captains chair, I ordered my vinyl from there too, so it would all match.