If they only include the longblock and tbey're used, 3k is really what you should expect to pay. ~4.5k is typical if it includes all the other stuff (turbo, injectors, manifolds, etc). Gruppe-s usually sell the blocks brand new with other stuff included, which is why they cost so much more (~$9k, NOT 15. shamrock's probably exaggerating). Motors lose a lot of value when used. Btw, not all ej207s are the same. The most common are the v7 and v8 versions, and they both have their differences.
One of the good things about the ej207 is it's a stock block, which means that it should perform in your car as reliably as it would in a jdm sti. That's one thing it has over built motors, which have their share of problems. On top of that they're easy to drop in (if you're somewhat competent you could do it yourself) since they're already assembled, and easy to tune (reliably) since you can source an ecu that comes with a reliable map that only needs minor modifications to run stateside. Also, ej207s have goodies usdm sti owners drool over, such as forged internals (v7), twinscroll (v8), big port heads (late v7? and v8), 8k+ rpm redline (I hear the v8 can rev reliably to 8.5k rpm!), semi-closed deck, and better avcs settings.
If you're looking to buy one, check here http://forums.nasioc.com/forums/forumdisplay.php?f=149
periodically. People sell them used fairly often. Otherwise you could pick one up from gruppe-s since you're relatively close by (they're in socal).