Well...I just picked up two Chenbro 48 bay top loaders (getting my 846s out of the rack) with an X9SRL-F motherboard for $400/ea shipped. That motherboard itself is probably ~$100-$150. So, the chassis really was $300ish shipped. And that has a proper SAS backplane (6gb/s), no eSATA stuff. That said, it'll require some surgery to put in alternate power supply(its), as the stock Zippy ones are trash.
Yeah, if you're having to pay for the Backblaze pods, the appeal sort of wears off. $599 will get you something newer and easier to use & manage as a single unit/low volume installation.