Update: spent 5 hours at the Charlotte airport trying to find the free shuttle to my $45 motel
Turns out the shuttle only runs every 90 minutes and stops at door B4, not the main pickup zone, so I dragged my bag around 3 terminals before a driver pointed me to a tiny sign behind a pillar, and now I want to know if anyone else has a trick for finding budget hotel shuttles without losing half a day.