Filling oxygen tanks

Santa's wife has decided that she would prefer that I fly with oxygen
even below 12.5K and especially at night. So I've been given a tank et
al. I was shocked today when I had it filled at Merucry Air. It is a
415 L size D tank. Because the pressure in their filling tanks were a
bit low, they could only fill my new tank to 1700 lbs, not to a fully
topped off level of 2000 lbs.
They charged me $40 flat fee..... a discount they said because it is a
small cylinder. That seem really steep to me.

Is this about right fur filling an O2 tank. I've heard that it is OK to
have the tank filled at other places such as with medical O2 or welding
O2. Is that OK?

Bruce McFadden Birmingham, AL
PA32-260 N5594J