LIS is much cheaper than MIL but everyone and their grandmother are coming to visit now, so flights will be expensive
Also, if you're looking at nonstops - you'll pay a premium as most traffic here is *A and TP has a hub in LIS.
In my non-objective view, LIS is much more interesting for a weekend than MIL+Turin. If you're into skiing, look into doing Milan and Turin in the winter, where you can get a good day or two of skiing in Via Lattea.