I've also hit up the Sundown yard sale. Ebay used to be a great source as well. But we will never see Lightning Audio neo motors going for $25 each. The last time I saw the Ebay price for one, I almost got rid of the 4 in my inventory.
I have build subs from scratch and reconed/refoamed. I use the provided rubberized CA glue for the spider to voice coil connection but that's it. I use E6000 for spider to landing and Ailene's for surround to frame gluing.
My custom subs:
15" Frankensub - A 90 pound Konaki motor with a 15" Ti frame and PSI soft parts. David from PSI built it to my specs and I picked it up at his shop.
12" car subs - A pair of Diamond Audio motors and baskets with custom recones from PSI. This is where I used my own gluing. One is in my wife's car and one is in my niece's car. Both with 1,000w amps. My wife abuses it worse than my niece and it is still holding up without issue.
18" IB subs - TC9 motors (with Elemental Design A12-22 stickers on them) and Fi Car Audio recone kits. I've tested them in the manifolds but never got around to installing them.
12" Frankensub - TC9 motor, 12" Ti frame and the rest of the parts from Robot Underground. This was my first sub built from parts.
12" Frankensub - This was an odd one. I had picked up some TC-2000 15" top assemblies that had the coil print into the aluminum cone. I removed the cone from the coil carefully. I then cut out the spider/coil from the frame as one piece. I searched for about a year and found a one-off 3 spoke basket with the correct spider height for sale at Car Audio Classifieds dot org. I used the TC-7 motor from the previous Ti frame as the motor and a surplus 12" cone from Sundown. The motor had a ton of copper on the pole piece and it ran distortion free. It was awesome. I traded it for an 18" TC-3000 (custom from PSI).
I still have some to build:
4 15" drivers with Lightning Audio/TC-2000/TC-3000 frames, Robot Underground spiders and spacers, Lightning Audio neo motors, Sundown huge roll cones
4 12" drivers with Elemental Designs AV 13.2 frames, Sundown huge roll cones, Robot Underground spiders and spacers, TC Sounds LMS coils and TC9 motors.
I build these for fun and to learn, not to save money.