So they sell you a $150 item...wait a while...then send you a bill for the $250 that it cost THEM to re-stock??
It sounds like they've perfected the art of "buy low...sell high"; but it's only working to THEIR benefit.
In all fairness, they might not be plotting evil things against anyone, but you should think about shopping around to see if you can get a more 'conventional' approach at another house. Maybe just that fact that you're concerned enough to look elsewhere will prompt them to take a closer look at their billing practices.
