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There's just no need for through-axles on a cargo bike... I also find tyre clearance perfectly adequate (I run a 32c on the rear, and you could go bigger by changing the mudguard), although to be fair I have a 406 wheel on the front, not a stock 451 (1.5'' tyre).
Vertical dropouts at the rear limits the options a little, but a derailleur is actually often the best option, since Alfine and Nexus hubs are not very well sealed.
As for the price, it's a niche bike, made in small numbers.
I'm not altogether sold on the aesthetics of the Bogbi, but will wait with interest to see what the price is. Looking at it I'm sure it's going to be at least the same price as an Omnium which is still my preferred option at this stage.
I'm sure I'm doing it wrong, but I have visions of setting the omnium up long and low like my commuter with drop bars and Thomson finishing kit.