I'm having trouble finding a NEW USGI quality magazine for less than $30 ($40 with shipping).

Is this the going rate?

Go to gun shows. Go to different promoter's gun shows. But yes, for NIB, $30-35 is as good as you'll get, IMO.

Ok - assuming you're not rich - and you want to
stock up on mags- this is what I suggest
( and what I am doing ).

Keep watching the EE board here - sooner or
later you will see some NEW mags for between
$25  - $30 - buy what you can afford.
( 5 - 10 - whatever )

Put them away in a closet.

NOW - start buying GOOD USED Mags off the board
for $18 - $20 - BUY LOTS.

You will probably never wear out 10 mags in a
lifetime.