This is a relatively huge deposit, agreed. We do waste a whole lot of helium. In fact, it may be that most of what's wasted is actually from natural gas fields not capturing the helium "byproduct".
I think you grossly understate that chilling it out of the air would be "signficantly" more expensive than recovering from ground reserves, it's far more expensive than that. A small helium recovery system for NMR/MRI instruments costs on the order of $200k installed, ignoring ongoing maintenance. We looked into one a few years back as helium prices rose - I manage 3 NMR instruments and we use ~60L/week of liquid helium keeping the cold - and the payback period for a recovery system at then current prices was on the order of 15 years again ignoring maintenance. That may be more like 12 years now. And that's for separating and reliquefying helium that's a very significant portion of the captured gas, not something that a small fraction of 1%. Economics get better as you use and recover more. I will say though that the newest large magnets come with built in reliquefaction systems - they still take several to many thousands of liters of liquid helium to cool and energize, but only require a small periodic topping up.
Pricing can be a bit tricky, but we pay ~$12/liter for liquid helium which is on the lower end of retail. One liter of liquid becomes something like 720 liters as a gas, so your per cubic meter price a couple of posts down is a bit low, it should be $15-20. A full party balloon has a negligible amount, though, if you figure 1/2 liter/balloon my one liter of liquid would fill almost 1500 of them, or about $0.01 each. I've filled a couple of dozen from one of our gas cylinders and the amount used didn't even register on the regulator.