Is the increased value coming from you? Or from the tool they purchased to improve your efficiency?
A dump truck driver doesn't necessarily get paid more than a taxi driver, just because he's hauling more material. It's all about the value you personally bring to the table, not the value of the tools you're using, unless it's a tool unique to you.
Well they probably do, as driving a dump truck takes more training and skill than driving a taxi. So it's a combination of the value you bring as well as the supply of other people who can provide that same value.