You can pay from £5 upwards for a server to be shown in the sponsored listing section. The amount determines the change of it appearing.
So if you pay £10 and another server pays £30 pounds, when someone opens the launcher, your server has a 25% chance of showing the other server has a 75% chance of showing in the sponsored listing section.
hey maca, i donated 15 pounds as of today, what do i need to do from here to get my server on that list?
By design A3Launcher is built to only show servers that it can distribute mods for, if the mod isn't available the server will not appear on the listings, you will have to make a request in mod additions to have it added to the launcher.