The "far superior pictures" of homebrews is mainly due to their using REAL cameras, whereas most commercial cams are using CHEAP "image processors". This is like the difference between the view seen thru a child's toy binoculars vs. a pair of Swarovski binoculars.
This is why a homebrew using a 4.0 mp Sony camera can produce better pictures than a Bushnell or other low-quality imager advertising 8.0 mp. Of course, there's no contest between the higher quality pictures of a 4.0 mp Sony cam vs. a 3.1 mp lesser quality picture from a Reconyx.
However, camera and imager issues aside, another limiting factor to picture quality is the outer (either clear plastic or glass) "window" of the housing. This is like comparing the difference between looking thru a plastic bag vs. a pair of quality eye glasses, between you and your binoculars.
But moving beyond picture quality, some of the high-end commercial cams (such as Reconyx) do generally have superior triggering systems for WHEN they can take a pic. Most homebrews have been using a "Snapshot Sniper" triggering board which is far superior to most cheap commercial cams and many of the ones in the $300 price range.
All that said, I've found "homebrews" to provide me a much better overall value for their cost, and be extremely reliable, year after year. By contrast, most commercial cams I've used have been very disappointing.