"He's a very authoritative news reader, but I wouldn't have thought NBR was that rich: To be able to pay a six o'clock newsreader what he's worth," he said.
NBR managing editor Todd Scott was unwilling to comment on paypackets, but confirmed the deal and said he and Dallow had been friends since meeting on the set of Lotto in 1997.
Ralston said it was likely the move would be viewed positively by Dallow's current bosses.
"TVNZ's management may well be thinking to themselves, 'He can front that because he'll get our brand out to business leaders'," he said.
The cross-network arrangement - similar to that for Mike Hosking who fronts both TVNZ's Seven Sharp and NZME's NewstalkZB morning radio show - was only confirmed yesterday following a meeting between the media companies' management at waterfront Auckland eatery Harbourside.
Dallow's move comes amid considerable tumult in the media industry as audience migration online poses challenges for revenue, blurs formats and has led to a host of new startups.
Last week TVNZ announced it would cut staff seeking to do "more with less", following on from a radical shake-up over at TV3 owner MediaWorks last year that saw plenty of established stars shed and its online, TV and radio news teams merged into Newshub.
Newspaper publishers NZME and Fairfax are both fully involved in producing video, and the Commerce Commission is presently considering a proposal from the commercial rivals to merge.
And earlier this month Newsroom, an online news site founded by former NZME and Mediaworks executives, launched.
The NBR has evolved over the past decade from a weekly newspaper to include a paywalled website with on-demand radio offshoots.
In January the company hired former Close Up host Susan Wood for its video arm producing short interviews with newsmakers, a unit Dallow is soon expected to front.
NBR head of digital Chris Keall said he was expecting an immediate impact.
"Things are still being finalised, but he'll likely be making a daily contribution. He's keen to mix it up and get out in the field," he said.