Maureen
I would do what Graham suggests and speak to the Manager at Cruise Kings. Ask him how he can help you make up for the fact that now they are selling this cruise for a lower price. I would ask him as your TA to contact Princess on your behalf. Say that you would be happy to take OBC in lieu of a cash refund. If they won't do that then ask if they will upgrade you to an ocean view room.
Don't email Cruise Kings but speak to him directly its much easier for someone to say no to an email.
I would also try speaking to the Customer Services Manager at Princesss.
If you still get no joy then my take would be to ask for an appointment to see the Hotel Manager. I often do this on the telephone from my room rather than going to the Guest Relations desk. They will probably ask you why but don't be put off by this just repeat that you would like an appointment.
I doubt very much that he will be able to give you OBC (I know of many people who are supposed to have OBC and it is not showing on their account when they board the ship. They have had no success trying to follow it up whilst on board but got it sorted out once the holiday was over) What he might be able to do for you is give you some treats whilst you are on board. eg Drinks wine etc. It depends I would not threaten to remove my tips as this can antagonise or alienate them and I find this is counter productive.
If none of this works then I would not let it spoil your holiday and just put it down to bad luck this time around. I have never had to get a price drop after final payment and this may be the sticking point. This is why I am suggesting OBC or upgrade as an option.
I did have a problem once with Princess in the Hotel they put me in in San Francisco was not up to standard. 3* when told it was a 4 * and really quite grotty. There was overbooking so they have and had to arrange an alternative so I told them I was checking out. I did this (it was commented that I was a very strong woman)The Reps said that they could not sanction the bill for the new hotel. This was not a problem for me I paid the bill wrote to Princess sent the bill and they refunded the money apologising that the hotel was not up to their usual standard.
Sorry I can't be more positive. Just feel you way and see how it turns out.
Good luck
Sue