$1000 is for brand-name. Used/imported are cheaper.
Refills of LOX are cheap, but you need to pay for the cylinder, which is expensive. At the end of the day you can get welding oxygen, which is exactly the same as medical/aviator. (And also you need to handle the cylinder safely)
Anyway, just start with Boost and see if it helps. They run out quickly, but nothing beats the convenience.