The profit calculation is seems like the ATR Buyout - Mats Cost.

However, if u post the item on AH, the profit is ATR Buyout * 0.95 - Mats Cost.

Is possible to add a option to show profit after the AH TAX.

I do not think the buyout - cost * markup is same to buyout * (1-tax) - cost.

For example, the Ragesteel Helm on AH is 100G, and the subtotal of mats (cost) is 80G.
You sold it on AH @ 100G, you will get 100 * 0.95 = 95. (5% AH Tax)
And you profit is 95 - 80 = 15.

I will submit a PR later.

I believe the plugin calculation for profit is actually buyout - cost * markup where markup is adjustable (the default value is 1.05). While not exactly what you are asking for, it should serve the same purpose.

All the pricing information is collected through plugins for Skillet-Classic. These plugins are distributed with Skillet-Classic but most of them were written by other people. I be happy to accept a modified plugin for your AH addon of choice.

You are correct, its not the same. However, it will take some effort to implement the formula you desire.

BTW, for your example, 100 - 80 * 1.05 = 16 calculated profit.

I have merged your changes and made a couple of minor changes. I moved the option above the sliders instead of below and I added a single constant for the 0.95. Thanks for your efforts.