Significantly cheaper seems like a stretch. 1200mg of Tirz is around $.20/mg, Reta is ~$.48/mg.
At highest published trial doses, that's a $2.76/week difference in cost, assuming you're buying in bulk to get the lowest pricing. $2.76/week is worth it to me for preserving an estimated 6-10lb of lean mass along the 80lb drop through GCGR protecting lean mass and providing more stabile energy for resistance training.
If I hit the same target weight either way, with Tirz I'd still have 6-10lb more fat than the same weight with Reta, not to mention the time it'd take to build the lean fiber back.
Energy levels for training compliance anecdotal evidence:
My first day taking Reta (No meaningful reta exposure) my walking heart rate exercising averaged 114bpm, with the average the day before and after being 115bmp.
18 days later, the same exercise now with more incline and less perceived effort has my average heart rate the past 3 days at ~130bmp with reta levels at 6-9.2mg (Tirz tapering 2.5mg to ~1.7mg).
I had no problems with Tirz, so far I have no regrets switching to reta.