I think it really depends on each person. For me, it's the comfort and style.
Almost of all of my work-shoes (closed toe pumps) are high-end because I really need the comfort. I work in downtown and walk around a lot, so comfort is key but I don't want to sacrifice style either. In the lower-end range, it almost always seems one way or the other - extremely cute but uncomfortable or extremely comfortable but ugly. Certainly not all high-end shoes are comfortable, but I find that styles that seem work-appropriate are extremely comfortable. My experience with likes of Nine West, Aldo (though not as bad as NW), and Guess were very negative and frankly I don't bother with them anymore. They have these plastic soles that I find very painful to walk in and my feet cannot breathe in these.
When my feet are comfortable, my days go by much easier - one less thing to deal with. The last thing I want is struggling to walk because my shoes are uncomfortable.
Oh, and I don't really worry about wearing them on the street. I mean, it's not like I intend to keep them forever. If I get a good use out of them for 5 years or so, that's good enough for me. Though I walk around on the street a lot, I take really good care of them and many still look pretty much new.
Finally, whether I can tell others are cheaply made or not... I don't know... I honestly don't pay much attention. If I looked super closely, perhaps.