andargor said:
Usually the market cost, sometimes the market cost plus components.
Actually, it's the other way 'round.
It's "Usually the market cost, sometimes the market cost minus components."
For instance, take a magical longsword +1. The Base Price is 2,000gp. The market price is 2,315gp - because you need to pay for the masterwork longsword, as well.
When enhancing it, you pay 1/2 of 2,000gp in materials cost and 1/25 of 2,000gp in XP cost, in addition to paying the 315gp required for the sword.
This means that if you take the total materials cost to create the sword (1,315gp) and multiply it by two, and the XP cost (80) and multiply it by 25, you won't get the same number.
This happens for any item in which the market price includes a component adjustment.
Take, instead, a wand of Identify.
It's Base Price is 1 * 1 * 750gp, or 750gp.
Creating it carries a component price of 50 charges * 100gp (for the expensive material component) = 5,000gp.
When creating it, you must provide all 50 pearls, but it only requires 375gp in magical materials (750gp / 25) and 30xp (750gp / 25). This all leads to:
Total cost to create: 5,375gp + 30xp
Market Price: 5,750gp