I had a thought that might discourage future problems like this.
Find two dirty four year old keyboards and take a couple of pictures of them to show the amount of dirt you have to clean.
Then clean the keyboard in two ways, keeping track of the amount of time you spend doing a 'just wipe it down' technique and an 'executive ready' technique. Make sure that you do everything needed to keep the keyboards functional, even if it adds time to the cleaning.
Once you're done, calculate how much it cost to get the keyboard 'executive ready' and still have it functional. Also calculate the 'just wipe it down' time. Then take the 'after' pictures of the keyboards.
I suspect that management will learn that 'just wiping it down' won't come anywhere near 'executive ready'. I also suspect that getting it 'executive ready' would cost much more than many high end keyboards.
You could even use the keyboards as an example of 'penny wise and pound foolish'.
You may even have some examples of losing keyboard functionality by having the letters rub off during cleaning.