Consider this:
A set of steelies is dirt cheap, almost free at a u-pull-it.
Your tires will last twice as long if they're only used for half the year.
So, the initial cost hurts, but it all works out in the end. Plus, your car will be significantly better in the summer, and worlds better in the winter.
Give this a read:
http://www.thetruthaboutcars.com/content/11457069861951095946/ 
