I would rather invest 10 x 60 Eur = 600 Eur every 10 years into new laptop or bigger RAM rather then trying to switch to non-free email and lose whole Google ecosystem.

Not having much spam is number one priority for me. 50ms delay in refresh rate is OK. In fact I have never noticed and it have never came to my mind that Gmail is slow. Yes, it needs RAM but I was never annoyed by any "slowness".