I am more suspicious of you than of ebay battery sellers; I have bought several batteries on ebay with no problems. Since they are so cheap, the most you stand to lose from a bad purchase is about $10, last time I checked the prices. Oh yes, you stand to lose if the battery explodes, but exactly the same number of cheap batteries exploding have been reported here as exploding Nokia batteries: zero.

One thing that makes me suspicious of you is the absence of quotations. I don't know what you said that made the dealer threaten to sue you, and I don't know exactly what the dealer said back.

In any case, the low cost involved makes this a tempest in a teapot, except tea might cost more.