IMO, a lot of the differences come from the different set of rules that govt work has to run by. For example, Aldi can just decide to hire a contractor that they know does good work at a reasonable price. In contrast, the govt has to use a lengthy fair and open bid process and if they want to select a bid that isn't the lowest, it's a painstaking process to justify that selection. Govt work must adhere to certain laws that tend to push up labor wages (see: Davis Bacon Act). Plus, the govt has lots of other competing goals, like supporting minority or veteran-owned business etc. A simple comparison misses all of those nuances.