Mr Key's response was: "You've got to dream big but it doesn't mean we'll be writing a cheque for that amount."
This morning while on Radio New Zealand Mr Finlayson refuted that the settlement invitation was a "cash offer".
"What we have said, is if and when the mandate is recognised, we will start negotiations and that one way in which we could do it is deal with the financial side first and then deal with cultural matters later on.
"It's no different to what I've said to other iwi around the country - there's no cash offer," Mr Finlayson said.
"It's really nothing more than, as it were, a call to arms. Let's get on with it guys, let's see if we can work through the various issues."
Mr Finlayson said he'd been working "very hard" on the mandate.
"I'm getting to a position where I should be in a position to recognise a mandate in the next little period.
"Then I'll say to people, 'right, if you want to negotiate, let's get going'. I've got a team of Crown negotiators ready to roll."
Ultimately, whether Ngapuhi wanted to settle was up to them, he said.
"It will be a very hapu-centric negotiation ... this is a very complex, a very large iwi, and a one-size-fits-all negotiation will not work."
Ngapuhi sub-tribe leader Rudy Taylor also spoke to Radio New Zealand and said there was currently a split between the iwi.
"It's not about the money, it's about resolving the issues that we have in terms of difference between the two groups."
Divisions arose around the corporate nature of the different runanga in the iwi and an income stream from a previous deal with Sealord, he said.
Ngapuhi's runanga chairman did not speak for a united iwi, Mr Taylor said.
"As the chairman of the runanga Ngapuhi, Sonny Tau, he's got to feel confident that he's got the rapport of the people, and yet that's the opposite."