Unless I’m missing something it looks like they’re not aimed at bikes. I just ran a quote on a roughly bike sized box (guessed without actually measuring one) at 31lbs (light) and if I got it shipped from Canada it should be about $1200, coming down to around $950 from the States. Doesn’t seem to make any difference if you put $1, $2000 or $4000 in the ‘declared value’ box.
If you were looking for this sort of import workaround, a return flight to Florida with a weeks car hire would still be cheaper enough to give you a couple of hundred dollars spending money… (idly quoted that with BA earlier in the week). Overall I think I’d rather have a UK warranty.