The p3700 isn't really designed for the average end user on price alone. It uses HE-MLC nand so will be way to expensive for most. The P3500 Should hit in the next few months though and it will be priced similarly to the difference between the S3700 and S3500. So probably around $1.50/GB or maybe just a tad more (vs the P3700 which is around $2.50-3.00/GB).
Most of these will be out by october I have heard.
The DC P3500 will be released at the end if August. I plan on getting the P3500 400 gig model. As for the P3700 and the P3600 they're already out. Here -