Emil Moe That's an interesting point and I do think I've seen PHP beat Python in benchmarks. But should that really be the main criterion? My intuition would be that architecture, caching and especially the database is the bottleneck for performance.
My first guess would be that development time is less with Python (that's been the case for me at least, and my impression is that Python is genearlly regarded as an easier and more consistent language than PHP). Saving 10-20% on development usually saves much more than doubling hardware would cost.
Some details... Does Django work with Pypy? That could be a substantial performance boost. There's also work on better async support for Django ongoing, not sure how far along that is.
Final note... If performance is the main criterion... Sure PHP may beat Python, but don't they both get obliterated by C++ or Rust?