The specs for HD-SR1 say that you get around 2 hours on the 30GB at 15Mbps (maximum quality).
Around 21 hours on will fit on a 320 GB drive, which retails for $90.00.
Which comes to $4.25 an hour, you can find miniDV tapes for slightly less than this, but there are multiple advantages to a hard drive (smaller storage size for example).

You can actually get 4 hours on XP mode on the HDR-SR1 so you might want to re-calculate the costs.

Based on a review at camcorderinfo.com you get around 10 hours in LP mode at 3Mps, XP is 15Mps hence the 2 hour calculation. Since it is VBR encoding how much time depends on the scene, I was erring on the side of caution.
If you are right Jack then $2.13 would be the price per hour of storage.