According to Tang Zhen's plan, after the warship was completed, the believers could buy it through battle merits.
Because the manufacturing process required a huge cost, if one wanted to buy a warship, they had to pay a huge amount of battle credits.
Tang Zhen wasn't prepared to earn too much in this area. Instead, he would give a reasonable price to prevent interested buyers from being scared away by the huge price.
In fact, after careful calculation, it was clear that compared to the possible benefits, it was completely worth it no matter how much battle merits they paid.
After the believers bought the warships, they needed to buy ammunition from Tang Zhen through the temple on the ship. This was another long-term stable income.