Puns that work for some do not necessarily work for all.
Here’s a witticism from a letter-writer to the Guardian a month ago. But I suspect that this pun doesn’t exactly work for anyone at all, though it is close enough for us to get it.
The Bank of England has a Monetary Policy Committee, which is in the news from time to time.
As we all know, money does not grow on trees, though if it did the tree it grew on would be a money tree.
The pronunciation of monetary is ˈmʌnɪt(ə)ri, with variants ˈmɒn-, -ət-. We can disregard the question of the vowel in the first syllable, which for some (most?) is the same as that of money, while for others it has the spelling-pronunciation vowel of monitor (which immediately destroys the pun). Let’s concentrate on the weak vowels. Is the rest of monetary pronounced as in money tree ˈmʌni triː?
Not for those who have a lax happY vowel, phonetically similar to KIT rather than to FLEECE (like me). For me, monetary ends with trɪ, which feels and sounds different from my tree triː. On the other hand my money also ends with ɪ, which I can readily identify with the second syllable of monetary. If, though, in the second syllable of monetary I had a schwa ə (as many do), rather than my weak ɪ, then that too would destroy the pun, because this schwa could not be mistaken for my happY vowel.
To make the pun work you need a tense happY (so that -tary = tree), but you also need a lax happY (so that money =mone(t)-). And you can’t have it both ways at once.
A strong, AmE-style suffix vowel in -ary destroys the pun, too, since tɛri could not be mistaken for tree. To save the pun you need not just to weaken but actually to delete this vowel, since təri could not be mistaken for tree, though tri might.
All in all, then, standup comics wanting to tell people a joke depending on this pun would have to be remarkably careful in their ‘diction’.