I have just purchased the pass at 34 euros.
I have now noticed that for a 2 day pass to the Colosseum, Forum and Palatine it costs 12 euro
If you count the discount of 1 or 2 Euro to the other museums etc and the travel (most things are within walking distance, or 1.5 euro each way) it actually means i have paid about 15 euros more than i needed to
You will also be very unlikely to get through to book tours on the telephone as they seem to be
permanently engaged at present, so getting the discount wont be worth it.
Book your ticket and the tour at the same time, save time, money and pulling your hair out...