Tourist season runs through October. For example, the rental rates in Venice don't go down until November.

We visited last year but I used award tickets. Can't help you on fares.

If you have the time to route through the UK, you might find it cheaper to fly to London and connect to a European Low-Cost Carrier (such as easyJet or Ryan Air) from there. The catch is that you need to allow ample slack in your connection time - the EU LCC's have absolutely no forgiveness about missing their flight for any reason. But October is when air fares to the UK drop -- I've gone for as little as $199+taxes (6 or 7 years ago).