Couch in Granada taught me what booking last minute really costs
Paid $12 for a bed in a hostel courtyard in Granada when the bus broke down, and the guy next to me pulled up the same hostel for $8 because he booked 6 weeks out, so now I actually check prices ahead instead of just rolling in.
Booking apps show you the price for specific dates, so I always pull up the calendar before I even decide where to sleep now. The real trick is checking a few different nights around your actual travel time, cause the same room can jump from $8 to $20 just by moving your bus day. I also started setting a price alert for hostels in whatever city I'm heading to, that way I get pinged when it drops instead of just hoping. Last minute can work in small towns or off season, but in places like Granada it's basically a tax on being unprepared. Learned that one the hard way myself, now I always have a backup plan hostel saved in my phone before I even get on the bus.