Ehh, even $4 a disc cannot compare with single layer, where even brand names are down to $10 for a spindle of 50.
The only thing the DL is good for is 100% backups of DVDs, and with the kind of compression technology we have nowadays, just squeeze them unto single layer DVDs. No way you can tell the difference on a regular TV. So I say use single layer DVD+Rs to archive those films you want (especially older ones), and wait around for next generation media (blu-ray or HD-DVD) movies to spend your hard earned bucks on.