Watchmen writer Alan Moore declined millions of dollars over his refusal to support Before Watchmen, he told Leftlion, a Nottingham magazine in a wideranging interview.  Asked "how much money do you think you’ve turned down for taking a moral standpoint on this," Moore responded, "Well, they asked me if they could give me a huge amount of money to bring out these Watchmen prequel comics—which they were going to do anyway—and that was probably a couple of million dollars." 

"You can't buy that kind of empowerment," Moore said.  "To just know that as far as you are aware, you have not got a price; that there is not an amount of money large enough to make you compromise even a tiny bit of principle that, as it turned out, would make no practical difference anyway."

Moore has called Before Watchmen "completely shameless" (see "Moore Says"), so it’s not a surprise that he rejected payment for the spin-off, but the amount had not been previously disclosed. 

Watchmen artist Dave Gibbons offered a lukewarm acceptance of the prequel series when it was announced (see "DC Announces 'Watchmen' Prequel").