High end private labels and niche markers. Mass produced and widely available are not your friend. High end older cockers hold it great (rippers/westwood/twister/DC1/DC2), private label stuff for mags, PL vikings/excals/Ms, KPs/Walz stuff. Basically, look at settled markets where supply is significantly lower than casual demand. I got my twister for $600. I've been offered over $1000, and offered a car for it. If you're going to spend a lot, buy stuff that won't be reproduced again.