This is easy, anything smaller than my round is for midgets, and anything over's a boastful lie.
Then there's the money angle, just under the threshold is a bit tame, but to go over and meet the additional expense probably needs another 20k before you are back into the clear water.The figure that this gives you becomes a bit hectic even for me, and holidays are just a nighmare...
It's a bit like being invited to carry away gold bullion, how many bars are nice to keep, and how many will rip the stitching in your pockets and fall out as you try a tip toe exit?
So simply based on this ceiling and what is physicaly possible,600, is probably a big round if the average is £15, and many -but not all- are 8wks.