Does anyone know the entrance fee when not used as one of the first two free entrances?
8.5 Euro, including the 2 Euro reservation fee.
Roger, the Borghese museum is well worth it. Amazing, famous works. Smaller than the Vatican museum, but I was more impressed with the Borghese, although I enjoyed the Vatican as well. Be alert to the time you are allowed there, it is limited and you cannot re-enter once you have stepped outside. The gardens are nice as well. Have a great trip.
Roger, just in case you missed this tidbit about the Borghese and the Roma Pass, you're still required to make a timed-entry reservation by phone or email. See the Roma Pass FAQ page:
http://www.romapass.it/en/FAQ/
And while I don't know how up-to-the-minute Roma Pass keeps it (prices can change at any time) here is a chart from their website that includes the discounted entry prices. Those would apply after one has used up their "free" entries. Dario added the € 2,00 reservation fee to the € 6,50 discounted ticket for the Borghese = € 8,50.
http://www.romapass.it/files/doc/SitiAderentiCostoBiglietti201809_eng.pdf
Thanks to each of you. I have already made a reservation by emailing [email protected] for zero cost.