I think we can agree it's a function of the greater surface area, and there's a mathematical formula to help with this.
But, I'd add that when I build larger-scale models (eg r/c models) I use different application scales - the paint's thicker on bigger models. Not a technique, probably almost a consequence of it just being a bigger 'object'.
Also - I must point out - my r/c stuff is scratch-built, and thicker paint hides errors and lesser-quality work!!!
To summarise, due to a range of factors, a 1:200 is going to need a lot of paint. Much more than a 1:350 model of the same unit.