[Solid Iron Bar] is a composite item. The materials needed to craft a [Solid Iron Bar] are 100 [Iron Bar], and they had to go through a process known as Smelting, similar to it’s real-life counterpart.
As this goes, the original price of [Iron Bar] will increase. The highest price for 200 bars was 50 gold coins. The price will fluctuate and eventually stabilize at 10 gold coins for 200 bars later. This is part of the game’s system to prevent gold coin inflation.