People today don't realize how cheap you can get a really upscaled machine. In Azure, a 48 core, 192GB machine is 2000 USD a month. This is nothing compared to upscaling your app on 10 servers and 20 services, with a lot of overhead, maintenance and dev time.

If you can get away with a monolith, it's the way to go, as long as you leave room to quickly grow horizontally as well, if needed.