Essentials Sell Multiplier

Plugin category: Economy

Minecraft version: 1.8.8

Suggested name: SellMultiplier

What I want: I would like when a certain group is given a permission they have a sell multiplier of say x1.5 when they sell something with essentials signs. I have looked this up before and this thread shows how to do it, but I don't know how to code. https://www.spigotmc.org/threads/modifying-essentials-sell-sign.151111/. Any help would be greatly appreciated.

Ideas for commands: none

Ideas for permissions: sell.multiplier

When I'd like it by: 1 week