In my opinion , there are a few reasons things are for the most part less expensive in the US
VAT is a big one, sales tax is anywher between 0 an 8% depending on what state you are in and there is no sales tax on most internet sales, also there is no tax on any item that you can eat or wear under $250
Petrol prices, even with the huge rise in petrol prices it is still a lot less expensive to transport goods here in the US
Volume, due to the large amount of people each retailer needs to make less money of each consumer in order to remain viable
in the case of pressure washers, I read somewhere that our 110v electricity is not as good for running motors as your 220v so we use mostly petrol driven motors , greater demand , greater supply cheaper prices