I thought that helium was in short supply. Would that make these things expensive? Also, I know they said it's quiet, but if the thing operates on a 60hz cycle, wouldn't that create a pervasive hum?

Helium is not really that expensive in small amounts and they are using it in its gas phase so it isn't much. Its needing enough to pump it around in liquid form for cooling that gets expensive.

Yeah, I was also under the impression helium was in very short supply. The article doesn’t mention that, at all. But it does say the unit is quiet because it operates at a constant frequency, so they can use noise cancellation very effectively.