Maybe you should just tell your mom now that you do not want to go on a cruise. Your mind is obviously made up because you are making every excuse as to why you do not want to go on the cruise.
For what it's worth, your expenses I believe are greatly exagerated. If this is a closed loop cruise (meaning that your cruse starts and ends in the US) you do not need passports. Also, if you want to do excursions cheaply do not book through the ship. In addition, my guess is that you booked a balcony room based on your $2300 for 3 people. I have gone on several cruises and have not had any additional expenses besides the original cost of the cruise.
I am not "bad-mouthing your character", I'm just telling it like I see it since you asked.