Well if you do what to at least have the discussion, one tactic might be to throw an optimistic-but-reasonable valuation at them.
"Yeah, that'll be $50 million..."
Then when they push back or ask for more info, just more or less repeat that and say you're too busy managing your growth to spend more time on it unless they're willing to move forward with an offer on paper. Just turn the whole thing around. If they go away, you're done (which will probably happen 99.9% of the time). If not, maybe you'll actually get it.
You could even pull the exploding term sheet trick backwards on them. "We wouldn't be interested in less than (insert biggish number here), and we'll need a response in two weeks." (Obviously word it more politely.)
"Yeah, that'll be $50 million..."
Then when they push back or ask for more info, just more or less repeat that and say you're too busy managing your growth to spend more time on it unless they're willing to move forward with an offer on paper. Just turn the whole thing around. If they go away, you're done (which will probably happen 99.9% of the time). If not, maybe you'll actually get it.
You could even pull the exploding term sheet trick backwards on them. "We wouldn't be interested in less than (insert biggish number here), and we'll need a response in two weeks." (Obviously word it more politely.)