I was going to emphasize this too.
I can't speak for all of "tech" as an industrial area, but in software development at least, there are also substantial indirect affects from the quality of work, some of which can be difficult to measure (without someone knowledgeable auditing work). Just because something compiles and produces the expected output, does not mean it handles corner cases well, or works every time, or doesn't have undesirable side-effects, or is easy to maintain, or that the design scales, or is forward-thinking in terms of technology choices, etc., etc. Getting all of those latter things might not be important in a few specific cases (eg: creating strictly throw-away demo-ware for marketing purposes), but in most business cases, each of them has a monetary value attached, and you could certainly be justified in paying more to get them.
Also, the point about competent foreign workers is well taken as well. To re-use my analogy, it's not as if there are not skilled foreign contractors also... but those people don't hang out at Home Depot, waiting to do day labor for under-market wages, they have higher paying jobs closer to home. The people who are being rented out as "cheap" foreign labor are, in most cases, "cheap" foreign labor, and you get what you pay for. It's just that in tech, more than other industrial areas, you generally get less productive value out of rote labor (in my experience).