Valuation question for link traffic

[Duckinla]

For selling/buying purposes, what kind of monthly valuation would typically be applied to revenue that comes from link traffic? I'm talking about parked domains that were picked up from drops. They apparently have existing links that generate the traffic. No TM's, no typos. But I can tell by the name and the lack of overture that none of the traffic would be type-in, it must all come from links. Any thoughts on how many months revenue that should sell for?