We have an original Nexus 7, and I have both Plan2Nav and MXMariner installed. P2N uses C-Map vector charts (app was free, all of North America East Coast and Bahamas chart package was $20) and the chart package has been updated I think at least twice since we installed it last November. AC data imbedded within (as Jeff et al have said), and updated periodically.
I think I remember seeing chart cost info on Jeppesen's website, even if it wasn't in the Play Store. I also see I have e-mail from Jeppesen suggesting periodic chart updates are at extra cost (50% of original)... but I don't have any charges like that hanging around, so can't confirm. And wouldn't care too much, anyway.
FWIW, MXMariner uses NOAA raster charts, and has been equally useful. Their charts are updated in-app quarterly (free), and the developer told me he's been considering a system of rolling updates, so LNMs are incorporated seamlessly more often. Sorry I can't find my receipt for cost info, but it wasn't much.
Another FWIW, we have both apps also installed on a 10" Samsung Galaxy Tab 3, no extra cost.
The larger screen is useful, but the unit is less compact... so they each have their pros/cons.
South River, Chesapeake Bay