The market variation from under $1 to over $5 per click is pretty accurate, if you are comparing a small city/town to a large metro area. Large metro areas generally have much more competition bidding for the same keywords. That's why I push my PPC clients in large, highly competitive markets to avoid the main metro area and target the smaller towns in and around the major metro area. The "casual" PPC using real estate agent generally goes for the large market and gets frustrated (and broke) trying to compete with everyone else. The "smart" PPC campaigns, targeting smaller areas within the metro area, with long tail keyword phrases and good, city/town specific landing pages, tend to be much more affordable, and produce more valid leads.

As far as managing PPC campaigns, once you get through the first 3-4 weeks of a new campaign, if it is set up properly, management should not take more than a couple of hours a week, mostly monitoring and "culling" non-productive ads and keywords. I find that constant fussing and micro-managing PPC campaigns is mostly futile. Reasonable long term average cost per click and average cost per lead are the main goals. If most keywords are costing around and under $1.00, and you have a few that cost $2.50-$3.00, but all of them convert relatively well, it's usually worth keeping the higher cost keywords active.

In general, a good average cost per PPC generated lead is $10 to $20 each, and can go to $40 per lead. I have clients in the same market at each end of that range, primarily because of wide variations in their keyword and landing page AdWords Quality Scores (Poor to Great), which affects per click costs, but also partly due to differences in their lead capture / forced registration forms and policies.