Just got an interesting email from tehmobius, the guy on eBay selling those 510 connectors w/nuts for a great price.
The connectors he's currently selling are nickel plated brass, but he says he can have stainless steel ones manufactured with a selling price of $5 each which I think is an excellent price for SS. The nuts would still be brass so they could be easily soldered. I don't know about others, but I really would like stainless steel threads on my battery connectors. They pretty much never wear out.
The problem is, it takes an amount of money he's not willing to put up to make that happen. Would there be enough people interested for a co-op? If 20 people would commit to 10 connectors each, that would probably cover it. I'll buy 20 right out of the gate.
BTW, he also got a shipment of brass ones so they should be available now (they were sold out for a while). They've been revised with improvements as well.