I've looked on ebay but the IB4200 are $65+ shipping there.

Thanks for the advice on Maxamps, the assembled IB4200 with Deans is 67.5$ there though.
I'd really rather stay under 50$, I guess IB4200 is out of the question at this budget? Do they offer better punch than IB3800?

However I'm intrigued by the 4k cells on Maxamps and ebay. They advertise them as 1.21-1.25 guaranteed which is much higher than any other cell I've seen, and much cheaper.
Why are they not more popular and so cheap then? Seems too good to be true... What's the catch? Not reliable?