My work box has in both metric and SAE, one set of: Westward standard combo box/open, Mastercraft Maximum stubby combo box/open, MAC combo ratcheting flex box/open flank drive, Sunnex offset angle open end, Mastercraft Maximum flare nut, Mastercraft Maximum s-type and c-type obstruction, Powerfist offset/step, Snap On Slim Low torque, Ultra-Pro big 1-5/16" through 2-1/2", Sunnex 1"-2" crows feet, no-name Chinese 7/16"-15/16" crows feet (badly need upgrade), and a bunch of random garage sale wrenches for cutting/bending/hammering.
I don't need duplicates of any one wrench because there are at least 2 suitable options for any task. I only buy a new style of wrench if I find I have to borrow it from someone more then twice.
I have 3 sets of basic wrenches at home, one in the house, one in the truck and one in the garage. When Canadian tire puts the SAE/metric Maximum set on sale for $40 it's hard not to be able to justify grabbing it, heck I have 2 extra sets still in boxes that I keep on hand for gifts. I have two buddy's who were always asking to borrow wrenches, I told them to bring me a flat of beer the next time they asked, I got beer delivered and they went home with wrenches, and got the hint that basic tools are a better investment then a night of drinking.