Melmoth makes an excellent point.
When time permits I respray locos and sell them on eBay, there's absolutely no connection between the time a project takes and the price it achieves.
It's purely driven by how much one (or more) people want that item.
Even "simple" resprays take 2-3 hrs work, if I was a professional model maker trying to earn a living doing this I'd have to charge a min of £50 per model (just for the labour, nver mind paints, decals etc).
Sometimes I get a mark-up of £10, sometimes £100 (great ), it all depends on who's bidding and how much they want that particular loco compared with the other bidders.
So, you have to remember that the price something like this layout will achieve is not based on what you and I think it's worth, but what someone (or some people) who would
love a ready-made layout will pay, several interested parties and you've got a healthy bidding environment...