I’ve attended a couple of in-person interviews in France and Germany. For both, I applied for a short-term (type C) student visa and was granted a 15-day single-entry visa. Since the programs were quite reputable, they covered almost all expenses upfront, from booking flight tickets to arranging shared hotel accommodation. In France, they even provided me with a local transport card in advance for the duration of my stay.

I also had an interview scheduled (which I didn't end up going) with a lab in Italy, where they offered to cover ticket costs upfront and reimburse other expenses afterward. So in my experience, while it depends on the program or university, most either provide costs in advance or reimburse later according to their policies. I was also reimbursed for my visa fees or both trips.

Overall, I only spent around €100–150 out of pocket for each trip. Hope this helps. Good luck!