Should PhD students pay out of pocket for their PhD expenses? Say a PhD student has a salary paid through a RA/TA or a fellowships but said student has no money for conferences, lab experiments, or to visit another lab for a few months to develop an important part of the thesis.

Should the student pay for these expenses out of his personal money? Is this acceptable, or should the student cut down on the project or change project to accommodate with the budget restrictions? 

EDIT: Think of students from small departments and from countries where research money is little to non existent
"Should" is a hard word here. I certainly never paid for these things, but my supervisor was well funded, and so I didn't have to worry about it. At the other end, I think a student certainly "can" pay for these things out of their own pocket. My recommendation for travel would be to avoid this by pursuing departmental, university, and conference-specific travel funds. 

I can't imagine it being reasonable for a student to purchase lab equipment. It's often expected that you'll have your own laptop, but workstations, servers, and compute clusters should be provided by someone else. Same for microscopes, reagents, glassware, and everything in between.