Maybe he had started to change in how he was thinking/feeling before the trip, and maybe it was that (not the camera) that was his real reason for thinking the trip wouldn't be a good idea. If he was planning to make a change before the trip he probably would have felt awkward or guilty going on the trip as if all was great. Maybe he didn't want to spoil your trip and planned to break up as soon as you got back, and maybe he thought that as long you seemed to have had a good time it was an OK time to break up. He probably knew what he was going to say but figured he'd let you tell him about the trip before saying it (out of trying to be polite and trying not to dump the bad stuff on you the minute he first saw you).
I suppose there's the chance he really did think having something "to keep" was a better way to spend money than "blowing it" on a trip; and maybe your spending your money on the trip "drove home" the point that you and he have different ideas about what to spend money on? Or, maybe he's someone who didn't like the idea of you going on the trip without him and that "drove home" the point that you're more independent than he likes?
It's all just guesses, of course. I know it doesn't help to keep this in mind, but whenever someone breaks up "out of the blue" the other person is usually hurt and confused. If nothing else, keep in mind that if things weren't what they should have been between you, better he break up now than let things go on and on indefinitely. For now, hang in there. See what happens. Either you'll move on or else there's the chance you may end up getting back together.