As a fan of epsresso I a absolutely agree with that fact that you should consider your own grinder and machine, but mostly for the massive increase in quality, certainly not saved costs. Even with second hand gear you are easily looking at an investment of 600 euro upwards. And as often, the sky is the limit. With the 0.3€ per coffee you mention, that's the equivalent of 2000 drinks, or 5 years of usage.

Also fresh high quality beans often result in costs per coffee a lot higher than your number. While I would encourage people to get into espresso as an hobby, I wouldn't recommend it to save on Starbucks cost.