On AUS-US routes, the difference between HQVW (SWU upgradeable) and STKL fares is obscene! You can get LAX-SYD for as low as $700-$900 roundtrip in S or K, but W fares are about $2500. Until about 6 or 8 months ago, I always flew on HQVW fares for way less than $2500. The gap between SWU-upgradeable and non-SWU-upgradeable fares is recent.

This falls in line with what is mentioned above, although different fare classes. Still, it just shows that United is tightening things to get more money out of people. It seems bad to us, but perhaps they just need it in order to survive.