In Bokun you should add your Retail prices to your Default Price catalog. The default price catalog is the one that you will use e.g. on your own website, so you want to have the prices that your customers should pay you.
Then you have the option of creating multiple price catalogs where you can add net prices. E.g. if you have agent with whom you contract in net prices, you can create a second catalog for him.
However, there is no need to create a second price catalog, unless you have sellers that should get other prices than your retail prices. In most cases you can assign your retail prices to your sellers, then you give the commission of the retail prices.