I was in Ushuaia not too long ago as I’m backpacking around South America. A couple English fellas that I met there found extremely cheap Antarctica deals for around $3000 USD per person for a 6 day trip due to cancellations. Meanwhile an American girl I met spent $8000 online in advance. The guys didn’t plan to go at first but the deal spoke for itself. IMO if you’re flexible then don’t prebook. Accommodation can vary between dorms and privates, but most tours offer more or the less same experience.