for the first 16 years I used them for blowing glass. Now I need them for sleep. What pisses the hell out of me is how Medicare payment is set up. Medicare pays $100 per month to rent a stationary oxy/con but they only cost $500-600 to buy. You can also get a great used one for far less than that. (That's a 5 lpm, if you need a 10 or 15 they are more expensive.) And, when you die? The company Medicare uses doesn't want them back.
My mom and a friend of a friend died. We called the number on the machine and they said they didn't want them back (oddly, same city but different companies) so they came to me for glass blowing. About once every 2 years I have to take them in for new filters (when the buzzer goes off) at a cost of $85.00.
So, if Medicare is buying them, somewhere along the way they (we) are getting ripped off.
Portable oxy/cons are a different matter. They coast $2500 for the best on the market. I just bought one when Medicare gave me pushback. So I thought all oxy/cons for medical use cost that much. When I found out the real price, and how much Medicare pays, I was pissed. (For craft use, you buy a used one that has been "modified". I honestly think the only modification is they have clipped the wire that goes to the battery that rings the damned buzzer telling you your machine needs service.)