Where are you buying these from? I've had a quick google and only see them on the bay for £500-600
Now to the bad news. Unfortunately I have my pc in another room and this has a rather long and expensive fibre optic display port 1.4 certified cable which should deliver 4k 144hz without issue. Has done 3440x1440 120hz without a problem. However it won’t do 1440 200hz or 240hz for that matter.
I’ve moved my pc and the included cable works fine so I know it’s not a monitor fault.
Which cable do you have and how long is it out of interest?