well...you can buy them on ticketmaster but its not always easy to get that many seats together (especially if the teams starts doing well). Last time I bought upper prime from TM I believe they were around $100 a ticket, and that was after all the various fees that come with using them. I would reccomend you check out stubhub.com, and see what you can find on there when the season starts. You will often find people that for whatever reason have several extra tickets, or even got them for free through friends or work etc. that are selling them at much lower prices than ticket master. I know last year was an exception because of how bad we were but I was able to get two second row tix, fins sideline for $40 each to give you an idea.
One last thing, if you are able I suggest going to stubhubs local pickup office if you buy from them, its right next to the stadium and will save you a ton of money in shipping fees.