I can reliably get about 11 gpt for a lux later in the game, or very early if it's Scotland (they love the amenities). I haven't crashed the game yet since discovering the problem since I've dialed back the number of individual deals. I think I can do up to and around 100 deals. I can try it in my current Rome game - I've got three friendlies with no bulk gold but gpt. But I will definitely save first - there's a chance the game may not reload!