Diplo favor didn't look like the largest offender here as that currency looks rather valuable when the WC comes knocking. Piecemealing out the strategics appears to be the issue here as Marbozir (in his Maori video) liberally dispensed his for large gold and diplo favor gains. I think he got 70 gold for 20 horses and 11 Diplo + some gold for 20 horses. It just appears the AI is very very generous with their currency for strategics and sometimes diplo. favor.