I agree with Rich if you are talking about internet based travel agencies or brick and mortar with large internet presence.
Most "local" TAs cannot match their prices and can only offer little goodies along with the standard Princess price.
That being said, Princess is becoming more competitive with their pricing as I am only able to save a couple of hundred dollars per person over the Princess price. Not like in the old days for sure when TA could give you prices that were 10-15% less than Princess.
I just booked a cruise the other day directly from Princess (first time) for me. I was actually surprised that they offered $200 p/p cabin credit that my TA didn't. Maybe they are changing their way of doing business & in the future I'll have to pay more attention to their specials I receive my email.