My used 17" alloy rims were $300 for the set of 4, plus $100 total to ship them by parcel post clear across the country. New ones are $600+ each. They required some corrosion repair, but easily pass the 10-foot test. Good enough for winter when they're usually dirty anyway. You can also get professionally refinished rims like these for, say, $150 $200 from various places. This gives some idea of the alternatives to the cheapo (and ugly) generic steel rims.
Besides, much is made of the performance and appearance advantages of alloy rims to get car buyers to pay more for cars with them. So why would these same people then happily use heavy ugly steel rims half the year?