Mobile workstations are serious computing devices with top-notch specifications, and as a result they come at a premium price -- the most expensive iteration of the HP ZBook 17 G6 costs £3,649 (ex. VAT; £4,378.80 inc. VAT) at the time of writing. For the money you'll get top-end discrete graphics, a Core i9 processor and a 17.3-inch screen with 4K resolution. Even as you go down the price and specifications list you get plenty of ports and connectors for using external devices, and there's even an optical drive. The entry-level ZBook 17 G6 model costs £1,609 (ex. VAT; £1,930.80 inc. VAT).
HP ZBook 17 G6 review at ZDNet