As far as I understand it, they keep what they don't spend. People are just perpetually undervaluing food and game advantages in the context of a million dollar contest. Tasha's "oh I was saving in case there was a clue" was bullshit, she gave up on her good strategy because she caved watching everyone else eat.
Anyway with Tony in meltdown mode but with 2x immunity, this end run of episodes has shaped up as perfect televesion. Really Tony and Spencer are the only ones whose games I respect, so hopefully one of them wins. Tony makes a lot of mistakes, but they're mostly rooted in his inability to read people. At least he's proactive.
Also, it's amazing that Cass can annoy the fuck out of me even when she's essentially endorsing my thoughts on Spencer playing that idol for himself instead of LJ. A college age male isn't the most selfish creature. If nothing else, clearly a human baby/toddler of any gender is far more selfish.
I bought Tasha's explanation. If there had been an advantage in the challenge and a clue to the idol, then she would have had a 100% chance of getting the next one, as opposed to just a 1/3 chance of getting the current one. But since she didn't have an opportunity to bid on food after that I guess we'll never know for sure.
I also respect the game that both Trish and Tash are playing. Trish changed the game 100% when she realized she could bring in Cass and then successfully was the one to bring in Cass. Since then she's been the one to try to reign in Tony (sometimes successfully, sometimes not). She's also played a really great social game. Who has she pissed off on the jury right now? She's let Tony take every hit, I have to imagine she's pretty well liked. As for Tasha, hard to argue with three straight immunity wins and while she isn't masterminding behind the scenes to the same extent as Spencer or Tony, she's doing her thing now and then.