Read that in a trade magazine but not clear why? Don't shops make more money on labor then they do on the markup on parts? If it takes 2 hours of labor to replace 2 quick struts vs. 3 hours replacing just the strut cartridges, isn't 3 hours labor more money that 2 hours plus a little more on the parts markup of the quick-struts? Labor is pure profit around $120/hour while parts profit is maybe 20 or 30 percent.