The most economical way is to use two KIT-059 boards (46x2 pins for $20 total). A good 3-rd party board with plenty of pins is FreeSoC2 from Sparkfun for $55.
I developed time ago a PCB with all pins of a P3 or P5 available (TQFP package). You also have in the board other connectors, I attach the schema. I did several protos but I haven't mounted yet (I hope not to have any error ). PCB measures 68.58 x 50.80 mm (2.700" x 2.000"). All connector are in a grid of 2.54 x 2.54 mm (0.100" x 0.100"), so it's possible to put in any breadboard. 4 layers, class 7D (Eurocircuits classification) For your cost calculus, 20 pcbs cost me 11.11 eu./board (net price)
If you are interested, tell me it to send you the files. Feel free to use
PSOC35_CORE_MODULE_V3.pdf 54.1 K
Thanks for the info. I am posting for another potential user, so will
pass this thread on to them.