Same here
Built models are a little like artwork when it comes to saleable value - how much can be realistically charged, allowing for time and materials involved, compared to what someone is willing to pay ?
If a model kit cost, say £20, and then there's a further maybe £5 or £10 or more in paints and other materials, and takes, say, 60 hours work, plus research etc, at what rate should it be charged per hour's work ?
Even at a low £5 per hour, with the cost of the kit and materials, that's £330 on average, quite a lot of money for a small piece of plastic, no matter how good the finished result.
I've often seen finished models for sale, supposedly 'pro built', at these sorts of prices, and many would not win many points in this forum's Group Builds. Whether they eventually sold at the asking price, I don't know, but even if they were very good, someone would really have to want that particular model to pay that sort of money.
When I've built models on request, I've suggested to the 'client' that they pay the cost of the kit and materials, and whatever else they think is a fair price - not the best business practice perhaps, but as long as my costs are covered, that's fine by me as, like Andy, I build models for enjoyment, and sometimes self-education ( learning more about the subject), and once a model is in the cabinet, it probably only gets looked at now and then.