They start at £250 / 275€ for just the portable pressure washer, its attachments, 1 battery & 1L of cleaner. Then, you can add in the extra water tank or dry bag in the next options.

Best portable: Sun Joe 24V-X2-PW1200 Pressure Washer - See at Amazon This Sun Joe ... There's also a built-in soap tank. The straightforward push-start button makes it really simple to operate ...