Actually the non mission BGs pay back 90-100% of maximum RS value of the particular level you kill. If you meet certain criteria: have your mission slighted, have invested over 50% of previous payout back to BGs, and are killing a level appropriately proportional to the RS value you have invested. There is no reason to climb to 185 BG unless you coin: you will need to engage in revival of dragons and occult and beast production to BG investment in order to maintain a high level payout. Or you can drop levels after each payout cycle for a period of time. The trick really is to find the BG level that your castle can handle. Your mission is moot. Even if your mission is 185, you can play for payouts at level 100 if that is what your castle is capable of: sapphires earned to buy back dragons during revival and production of beast/occult ability are taken into consideration here. World top 200 BG ranking and top ten trophy winner. I won my trophy with a 19.99 pack worth of sapphires at the start of the BG week. It's not difficult if you play to the math! It's a game of code: 1s and 0s, you just have to do the math to play them well. There are plenty of RS value: BG level tables running around on LINE app.