Exactly.

I think it would be more like people will answer more honestly when they pay a small 5sat zap to make their choice.

I think it should have fixed 1 sat to vote by default.

Isn't that how all polls work?

Zap polls only make sense for something like a fundraising contest.

How else could they work?

Unless you limit votes to, say, people you follow there's no way to avoid Sybil attacks.