All good questions... while I'm not much impressed with the latest leadership of AOPA, they have a website that may answer some of the questions you pose.
http://www.aopa.org/letsgoflying/
Many of the items are "unanswerable" because while there may be regulatory minimums, say on how much one has to fly to maintain currency to carry passengers, the rules may be completely different if one is by oneself in the aircraft. Aviation is mired in regulation but most of them track back to something that makes sense, like... higher standards if you're flying passengers other than yourself.
It's not cheap, and it's not always convenient... it's more a lifestyle than a replacement for the airlines for everyone. But for the few who enjoy the challenge, it's pretty sweet to just open the hangar door with a key and head off somewhere.
Like a lot of things in life, the resources to do it must be taken from somewhere else, so not too many active pilots are driving new cars, buying the latest gadgets, etc... sure there's always some in any group that are wealthy enough to do that, but most sacrifice significant things to do it. Same thing with race car aficionados, computer geeks who need the latest-and-greatest, campers who buy house-sized motorhomes and the fuel to operate them, etc. Similar fiscal discipline required.