What would completed Zoid models be worth?

Considering how old they are now, they probably aren't worth too much. Zoids really didn't take too much ground in the US market Canada as well. I do also own 1 Zoids kit myself, Gravity Petra I think so. I got for Christmas and it's pretty much trash as lot's of stuff is missing. If you are planning to buy more, than to me it seems you still are fond of them so selling all your older one wouldn't be the way to go. Now Wal-mart and Toys R Us has stopped selling them long ago, your best bet is probably www.hlj.com because in Japan they are still a big hit, and hlj still stocks up on news ones too. Their shipping is pricey but it depends on which method you choose. In overall Zoids that have been made for many years aren't going to be worth much, and hlj.com is your best bet.