Who says you need to win? You just need to ensure you don't get a 3rd game, which, in the OP's case, should be extremely easy to control, be it losing both or winning both. He clearly stated from the beginning that teams in his league can't demote. Besides (see below) you're still better off with 6th and 3 relegation games than ending 5th even in the event of selling everyone.
It's only relevant in the circumstance that hrudey pointed out as we have discussed. There is the possibility that if you lose a relegation series you are treated as "demoted" the following season and you have some hit (difficult to quantify) to your earnings. However with 130k extra cash you will be able to build seats (650 bleachers or 186 lower tier) and that should compensate. Clearly winning both games would be ideal.
Look what happens with a 3rd game:
6th_ +177k in the first week, then +74k+87k-174k=-13k in the second week. Total +164k
5th_ +33k in the first week and +74k in the second week. total +107k
This is really simple math. People should be able to apply the relevant numbers to their own specific situations. As I said, if unlike the OP you risk demoting, you should just go for 5th.