Point of order Mr. Chairman.

Basic education?
Being of a naturalIy stirring disposition I recently found myself penning the following:-
"I think you/your staff may need lessons in either English OR Arithmetic.

I spotted a rather "beat up" looking Echeveria at your ******** Dept. on a "stall" bearing the sign "All at 1/2 marked price". 

Unfortunately I am unable to append photographic evidence, but the item was marked as £14.99 down to £10.49.
Since even MY mediocre arithmetic is up to spotting that £10.49 does not even CLOSELY resemble 1/2 of £14.99 I presumed the "marked price" was in fact  £10.49. 1/2 of which would be, near enough, £5.25 yes? 
I was sufficiently gobsmacked at being charged £7.50 that I returned the plant to where I found it. May I respectfully suggest you rephrase to "Half ORIGINAL price" OR If you choose to use the wording "Half MARKED price" you do, in fact, charge half the MARKED price?"

OK, grump over, back to your cuppa, pint, Prosecco, whatever, etc.