On the subject of the meter, it's not just the cost of installing. You have to get the details from YOUR water company. Most usually have a minimum charge per month for each meter. I know our city it's something like $8/month, and that pays for the 1st 5000 gallons of water. But if I only use 1000 gallons in a month, I'm still charged the $8 minimum.
I know that in my case, when I ran the numbers, I found that the saving in sewer charges during the summer pretty much matched the cost of the minimum during the winter. (I also later found out that you can get the service for the 2nd meter turned off during the winter months).
On your choise of main line pipe, I would recommend you upside to 1" PVC. There isn't much of a price difference between 1/2", 3/4", and 1" PVC pipe and fittings. Yet a 1" pipe has twice the capacity of 3/4" (or only 1/4 the pressure losses). You don't see a (relatively) major difference in prices until you get into the 1-1/4" stuff.
I'd also recommend you look more into 10"-12" deep for burying the pipe. The deeper, the better it's protected (from both unexpected cold temperatures, but also from any "heavy" equipement that might ever come accross your yard.
Better yet, I'd suggest that you spend this fall and winter reading over the web site
Irrigation tutorials.com. It's loaded with lots of good information, and you've got the time to try to digest it.