Looking into how much ads pay in general, taking into account the amount of active users and other variables/assumptions,
Affording better servers is a matter of time, seeing that the devs have always been trying to improve the quality of their service, with or without ads and subscriptions. When it comes to time, patience is key.
Yas and ShortCode I have experienced a few slowdowns in speed that I don't experience with other apps. So I'm being patient and waiting for the Sololearn devs to hopefully improve the app in time. I wonder if the Pro users have a better experience than unpaid users in terms of access speeds.