This quote is taken out of context quite often, Franklin was talking about money and taxes, and actually paying for security of the people, not the liberty and freedom, I think you are implying.
And the majority historians believe he was implying based on the entire letter, almost opposite of what that quote implies on its own.
The majority of historians say this:
At the time, the legislature was trying to tax the Penn family lands to pay for the defence of the frontier, during the French and Indian War. However, the family was unwilling to have any such law passed in the assembly. “Franklin felt that this was a great affront to the ability of the legislature to govern. And so he actually meant purchase a little temporary safety very literally,” said Wittes, as the family was trying to give a lump sum of money in exchange for the General Assembly’s acknowledging that it did not have the authority to tax it.
https://indianexpress.com/article/ex...-8697766/lite/