These are high-quality ENIG proto boards. The combinations offered allow easy prototyping of various surface mount designs before committing to a PCB prototype run. The extremely low-cost pricing makes it painless to try out multiple circuit designs.
These boards had such a low price I wasn't even totally expecting them to show up. They did show up, quickly, and they're awesome. Great quality and finish, no problems soldering. The stacking / interlocking modular design is ingenious!
I can make as many soldered prototypes as I want now without feeling guilty about the cost of boards.
It would be really cool if the store carried matching sets of headers and M3 hardware as well.