Electrical Trade Service Pricing

I am trying to put an agreement in place with our preferred electrical contractor. They would like to bill me for materials at Trade Service + Mark-up. Does anyone have any insight on whether this would be a fair arrangement and what the benefits are?

This has probably been actioned. My experience with electrical trade pricing is that it is generally higher than that for which you can purchase material(s). It is an average price and, if I'm not mistaken, they add a % to that price.