In the uk cost would be around the £150-£200 i think.
Nat, no, this rolling thing just carries water, but that's all the freedom trolley etc do, albeit with a pump/battey, not exactly difficult to lash together.
Whether trollies are much use beyond extremely rare instances of poor access is debateable anyway. I wouldn't touch a trolly of any kind as they are a waste of money. But if you must have one, I'd go for this camping one at £40, add a pump (£100) and battery (£50) and it's still going to touch £300++ with hoses and fittings and stuff.