As mention, the few times I have been in a high pressure situations, I tell them I never decide for at least two days. In one case I stopped the sales fellow and asked what language we were speaking.
To his blank stare, I followed up with " I thought it was English but If you like we can try pig-Latin, it is the only other language I know." He got the point.
I have no problem treating stupidity with sarcasm. Trying to sell me something I do not want is the height of stupidity.
Fortunately, I rarely find myself in those situations.