20-30% seems pretty high for customs fee. also based on some basic research it looks like anything below $2000 is allowed as informal entry.
https://www.cbp.gov/trade/basic-import-export/internet-purchases
good news for Zap specifically is that it looks like they marked the value as $100 (actual value was $1k) so it got to me with no customs issues. they had lightning shipping too, ordered on Sunday and received on Tuesday
so for anyone on the fence with Zap, i say go for it! props to dude linking to their website here.