What an odd reply. Was it intended to support or refute an assertion about maturity?
However, since you chose to prolong the thread, let's recap....
Mr.Jeffrey chose a public forum to initiate a discussion about his prices and profits. The conclusion so far is, that taken with his ability to reduce the price by £30 EVEN THOUGH HE HAS THE EXTRA £800, OR SO, COST OF ATTENDING AN EXHIBITION, that normally his prices are too high and could therefore be reduced by £50 or more.
Mr.Jeffrey, in a frank and ingenuous exposition, contributed to the discussion that his mark-up is 150% which is gross under any circumstances. Profit margins on goods are usually less than 100%, and so there would seem to be scope for a reduction of £80 or thereabouts on normal, non-exhibition days.
Perhaps there is a moral here, and that is not to use a hobby NG for commercial advertising?