It is appalling what it costs to maintain the various databases associated with flying my own aircraft. I have a panel mount GNS 430W and a couple of handheld GPS's.The 430W not only needs the NAV DATA updated, it also has a terrain database that needs periodic up-dating.
I have avoided buying an electronic flight bag for exactly this reason. When you buy one of these systems, you are "married" to that format"...better, or worse.
As more and more aircraft are equiped with "glass cockpits", the costs go higher and higher, not lower as economy of scale would suggest...what's going on with that?
Jeppesen has the inside track on providing the actual databases in the various proprietary formats, but I would highly suspect (and this is just a guess) that there is a cozy little kick-back from Jeppesen to the manufacturer for each subscription/up-date.
The FAA is a tacit supporter of this data cartel since one cannot legally shoot a GPS/RNAV approach using an out of date database EVEN IF THE SPECIFIC APPROACH HAS NOT CHANGED and matches a previous one in every respect. Don't get me started on why the costs for a single update or subscription are outrageous.
Personally, I would love to see AOPA, or some other pro-aviation organization provide data-bases. Seems, just like single FBOs on a field, Jeppesson needs a competitor.