However, when you look at the shop systems of most games you will notice that most items sell for WAY less than you could buy them for. A Most video games do this purely as a balancing mechanic, but there is a real world explanation for how this kind of thing sometimes happens.
In many games, a \$1000 sword may only sellssell for \$100, even when you are selling it right back to the guy you bought it from that same day confirming. This confirms that craftsmanship is not the guiding principle here. HoweverHowever, in the real world, wholesale is typically 50-85% of retail meaning that the guy who actually made that \$1000 sword was paid by the shop owner \$500-850 to make it. Videogames general do not define these values so we will assume the real-world values here.
So the real question is, why would thea shop owner pay the blacksmith up to \$850 for the same sword that he would only pay you \$100 for? You see, the shop owner can not keep high quality wares in stock without the blacksmith; otherwise, adventurers would just always buy his best stuff and fill his shop with worthless junk they are selling, and his shop would very quickly be filled with nothing but a giant pile of worthless goblin spears.