well it ain't a privilage - there really is no other choices - sometimes they have a special train that will run from Boston - but usually that is only for certain games so forget about the concerts and you have to arrive and leave at a certain time.
There really is no other option - there are some businesses that you can park at - but some can even be higher. I did an on-line search and found one for $60. Usually you have to park a mile away and pay $30 or $35 at a business. So the businesses can do so, but the poor residents can no longer.
We checked into limo/car service, thinking we would only need to pay for the driving time - but no they charge you per hour through the show - I guess they just sit there.
Last year we stayed at a hotel nearby (we had enough points to stay for free). But we waited too long (with our move and stuff) and so the only place to stay is a good distance away.