Reaching the eighth-finals of Champions League and being eliminated: worst case scenario
Finishing second with four draws and two loses will grant you 4x0.9 = 3.6 million euros.
For reaching the eighth-finals, add 9.5 million euros.
So, the team will earn 13.1 million euros.
Finishing 3rd in group stages, then winning the Europa League: best case ...
No, it's probably not worth the risk.
Reaching the knockout stage of the Champions League alone is worth 9.5 Million €, even if you get knocked out directly. Also you get a piece of the big cake... TV money and some cash based on the team's UEFA coefficient.
In the Europa League you'd have to reach the final in order to make that much money (~ 10 Million ...