Looking at Ensure, it's $42.50 for 24 bottles with 350 calories each. At ~2000/calories per day (6 bottles), it looks to be something that would cost ~$320/month to replace most meals with.
I'd imagine that Soylent's sales success will lie with its price point reaching around ~120-150/month price point. Going much higher than that, and the financial incentive would be lost.
$42.50 for 24 is just sloppy shopping. I get about half of my intake from Ensure (and its competitors), not by choice but because of a medical condition that often precludes normal eating, and $28-32 ($7-8 for a six pack) is an easy target to maintain consistently. The cases of 24 are aimed at institutions, are priced accordingly, and never go on special.
I'd imagine that Soylent's sales success will lie with its price point reaching around ~120-150/month price point. Going much higher than that, and the financial incentive would be lost.