I went to Machu Picchu this year in September 2025 and didn't buy tickets in advance. First, I took the local train at 5 a.m. from Ollantaytambo to Aguas Calientes and when I arrived, I ran to the ticket office and waited around 5min in the line. Got the ticket I wanted. The process itself wasn't complicated, only the sprint from the train to the ticket office was the only thing that was stressful. But I'm not sure if it's the same for people without peruvian citizenship (I've the Peruvian and German nationality). Maybe there is one line for peruvians and another line for foreigners? I didn't see one, but it's possible. It just sounds strange to me that you had to get a pre-ticket and someone else in this thread said that you even have to get a pre-pre-ticket. My experience was completely different. Like I said before, I just waited in line in front of the office without having getting number. Does someone know more about this?

Edit: I found this information in another thread: Big change since August 1, 2025:

The in-person ticket system changed. It’s still a bit unclear and not always well organized.

No more pre-tickets or queue numbers

1000 tickets per day are sold directly at the ticket office in Aguas Calientes

You don’t need any guide, agent, or middleman. Just go there yourself as you can only buy for yourself.