Aren't you losing too much space if you don't have shelves?

We could have palletizable and non-palletizable items. My concern is that it sounds like we can't reliably lift these things [heavy and bulky items] in a way that makes sense. Shelving is not useful.

Why do you have to be four shelves high to break even?

It's about space efficiency. Your aisle has to be wide enough to accommodate the robot lifting these pallets. The more pallets you're handling, the wider the robot gets. If you have three pallets, you might be able to get one that drives sideways to improve space efficiency. But if you're straight with a wide load, the aisle needs to be that wide. You're only going to be able to load on both sides. Let's say we're doing three pallets wide on a single unit. We might need to add one more pallet to give us rotation. It might be a bit more, so it could be less space efficient. That gives us four pallets for an aisle that the robot has to navigate. Each shelf is only two pallets wide. If we go up to a three-pallet size, it would be a two-to-one ratio. Previously, I thought it was four-to-one because of a smaller setup. With this, you could do it two-to-one. They only need to go up one level if you have a bigger setup.