a good comeback to someone who said "your talk is cheap!"?

'The cost of your needs would dwarf the national debt'

or

"The credibility gap between what you say and reality is measurable in light years.'

tell them that they obviously have never had to stand up and speak up for what they thought was right when it wasn't popular.

say, my talk isn't cheap, it's free your not paying for me to talk, right

your vocabulary is limited