I have for sale a barley used portable oxygen concentrator that was bought maybe 3 months ago and barley used. It was purchased from Alex home medical for about $3000. It was used by my late wife the few times she left the house.
Unit is a Inogen Rove 6, with the extra long life battery and weighs about 6 lb. It includes the machine, the carrying case, a charging cord for the house, and one for your car (plugs into a cigarette lighter plug).