They're worth what you can get for them.
That said, the US coasts (east or west) tend to be higher than the center of the country. I live on the west coast and I tell people running models start around $5k, give or take. Any mods can add, but like all mods, not nearly as much as they cost you. There is no way I will ever get back the $$ from my truck that I've put in it (I can still dream though). The interior of the US, prices are like half, it seems.
If you're a master mechanic and your brother-in-law owns a CNC shop and your father used to sell military parts, you can expect to break even or make enough money for a latte - from Dunkin Donuts, not Starbucks.