We are visiting Stresa, Italy on the way to Zermat and it appears that there is no way to avoid expensive rail seat reservations (we have rail passes). In fact, the Milan-Stresa leg (less than an hour) costs more than the Nice - Milan leg. I haven't even priced out the Stresa - Brig, Switzerland connection - I'm afraid it too will be expensive. Is there a way to make this linkage without the high fees for seat reservations?
Not sure where you are finding your price for the Milano Centrale to Stresa trip, but it is very inexpensive with no reservations required. On the Trenitalia site there are two different types of train you can take at either 9 euro or 4.95 euro. We will be taking this very route in early July and have all the info printed out. Trenitalia will be revising their schedule sometime in mid-June so perhaps you are looking too far ahead. Try a date before mid June and you should see the correct costs.
If you take a regional train from Milan to Stresa, no reservation is possible. If you take a Cisalpino train, buy your seat reservation in Milan for €5.
It also will cost €5 for any leg on a Cisalpino train between Stresa and Zermatt.