The "poor boy" gun, for the most part, is a 19th century thing.
In the 18th century, all guns had hundreds of hours tied up in them. A gunmaker may have bought some parts, but those parts were still handmade by somebody.
The various trade guns were the most cheaply made of their time. But on the whole, a basic fowler/rile had a bit of carving and engraving. To us, it may seem fancy or unneccessary on a basic gun, but at the time, labor was cheap and materials were expensive. The opposite is true now.
All guns back then were meant for "daily" use. But not all people had to use a gun every day.
When you say "from scratch", does that mean a forged barrel, forged lock, etc? or just parts and a blank of wood?
Mario