Are cheaper rotomolded coolers just as good as Yeti?

Probably yes. A cheaper rotomolded cooler from RTIC, Pelican, or Orca will keep ice just as long because the performance comes from the rotomolded construction, thick insulation, and rubber gasket—not the logo. Yeti’s main advantage is customer service and brand cachet, so unless you need a no-questions-asked replacement for heavy abuse, save the hundred bucks.