1911 manufacturers are not the only ones using MIM parts or otherwise looking to lower costs. Find me ANY gun manufacturer who hasn't had a gun come back for a defect or breakage. I'm positive you can't.
The advantage of the 1911 platform, as I see it, is that replacement of MIM parts is extremely easy to do for an amateur. I have no experience with Glock, Sig or HK, but I know that I cannot replace the internals on my Walther P99. If I wanted that done, I'd have to send it to Smith and Wesson or to a gunsmith. On the contrary, with my SA GI, it took all of a couple hours to learn how to completely strip the pistol, and took around $40 to replace all the MIM with "better" parts.
I put "better" in quotes because I am certain that companies such as S&W, Springield, Kimber and others would not use MIM if it was as bad as Old Fuff and others on this board say it is. The majority of SA guns contain at least some MIM, and if it was so bad, their reputation would be trashed (same goes for Kimber and S&W). These companies have not spent the last 100 years building a great reputation only to ruin it to save a few dollars. I replaced the parts mainly to do it, for the learning experience. I have not replaced any parts on my TRP, a much more expensive gun, but one that contains some MIM parts.