The value of the tag is likely to be approximately $3m.
Earlier in the offseason, I was asked if the Jets could place the franchise tag on Folk and my response was this: "No chance". Shows what I know!
It's possible the Jets could have put this down as a placeholder so that negotiations on a longer term deal can continue beyond the start of the league year, which is what they did with David Harris back in 2011. Ordinarily I'd say that $3m is decent money for a kicker, so Folk should choose to take the money this year and hit unrestricted free agency again in 12 months, but there have been a few bigger kicker contracts dished out recently. Carolina kicker Graham Gano got a four year deal that averages more than that earlier today, so it did start to look like things might be headed in this direction.
I'm not generally a fan of the franchise tag, other than as a mechanism to extend negotiations or facilitate a trade, because of the lack of flexibility a one-year deal provides. However, with the recent reports of the rising salary cap, I don't think cap flexibility will be a concern for this team for a few years.
If the Jets were to negotiate a longer term deal with Folk, they would definitely need to guarantee more than the amount of the franchise tender to get Folk and his agents to sign. That could in theory reduce Folk's cap number for the 2014 season, although that's not necessarily a primary concern.