Of course he's concerned about her feelings. He's giving her a D810. Playing a joke or prank on somebody you love doesn't necessarily mean a lack of care for the other person's feelings. After all, after the initial shock he was going to immediately show her the new camera. However, he asked for our advice, and I think the best advice is not to disparage him but to encourage him to skip the prank and merely do a switch of camera and have her be surprised to get the D810 in return for the 7200.

Several posters on here expressed their opinions in an adult manner. Many resorted to childish behavior. The cowards who hide behind their keyboards and deride others and call them names remind me of lynch mobs and Antifa protesters. Put them in a group and they're Bad A33gs, but by themselves they're Cowards. A sense of humor requires intellect, the ability to take a joke requires good self esteem. Most of the posters in this thread have neither.
I don't know whether the OPs idea is a good joke, that depends on his daughter and their relationship. But the postings on here attacking him are made by a bunch of W.I.M.P.s, who never had any guts until they could hide behind their computer screens.

RE: "He just didn't get the feedback he expected".

Actually what he asked in the last sentence was how long should the "joke" last. First, he had her thinking he got a new camera (sounds like he thought that would be enviable), then he immediately replaced the one he flung down a cliff with his new camera (sounds like he's now Prince Charming), and his ending question was how long should he make her feel bad for taking his new toy (if she did accept it), before exposing the trick.

As I think further about this, it sounds as if he just wants her to think he's gallant and wonderful. What we've reacted to here is his confession of jealousy, which is what people feel when they are insecure in a relationship...feeling inadequate and needy. That idea would be reinforced by his view of her as lovely. I can see how some would react to this chord, and defend him.

While we can understand it, this behavior isn't healthy unless they both understand why they play their respective roles in these "pranks." He will constantly be manipulating her for her dependence on him and she will constantly be proving herself as independently worthy of his love. If they DO understand their roles, and they might...after all, he IS taking her on a two week shoot in Paradise...then...the object becomes balance.

Does her competition become his humiliation? At what point does his prank become an act of terror? He's asking us for balance and seems to realize he's at the brink of bad. Dad! Manipulating her feelings creates a continuing barrier! If your daughter is gloating in her talent, its your job to teach her grace. But if she's just good, learn grace yourself.

And now we are getting somewhere , so that's your underlying problem all along ,bam you said it all in one sentence above , you defently
Need help , you took it upon yourself to base your whole argument on your judgement that he's childish ,selfish ,there for your condemning him , for one thing you don't know any of that , like I said before who made you judge and jury , you should see a shrink there may still be time to get back on track , you just made all that up in your own mind to justify your outlandish conclusion you settled on, you need a lot more info to come to that sad end , your a sad sample of a caring human, you have more issues than any one here , and you can't even end see that .