Does anyone know if there is a formula or an equation for figuring out the purchase price of a magic item? (the chart found on PHB pg 223)

I'm trying to come up with a "Net-Worth" on my players, and other than doing a look-up I can't figure out how they come up with the numbers.

I'm trying to come up with a "Net-Worth" on my players, and other than doing a look-up I can't figure out how they come up with the numbers.