I don't think that there is only one answer. It depends what your are doing on Mecabricks.
Probably not much compared to video streaming for example but a little bit more than reading a news website.
If you just build in the workshop it will be very minimal but a little bit more if you open a lot of big models in the player.

All of that to say that it is definitely not GBs but probably more MBs.

Ok, thank you.