Used CD's are the way to go.
As for why CDs are cheaper their first week, here's why:
- Record labels try to sell all their available copies of the new record (at a lower price)to their distributor, who in turn sells them at a reduced price to the record stores.
- Before the release date, the record label tries to aggressively promote the album.
- Thanks to the lower price, the retailer then sells the album. The retailer will then go to reorder the album. Based on the sales of the album (meaning if it sells well), the label/distributor will then sell the album wholesale for a higher cost to the retailer.
The stinky part about the music industry is that retailers cannot return copies back to the distributer the majority of the time. That's why you see retailers stuck with so many copies of the last Korn album. It's first week sales were pretty good so they reordered a bunch, but they didn't increase and wound up paving the walls with Untouchables.