Well I don't know what your winrating is but I'd say 150 GE is all I'd win with those wagers as well because my winrating is 55%-60%
Ofcourse I almost only play tanks and I don't know how much higher the winrating can get in planes
The whole problem is that wagers are applied to the Random battle mode, even if you are a member of a 4 man squad you can't expect all members of your alliance to be communicating and playing the team game. This means that a 'Wager' is a gamble, you are gambling on the ability of everybody in your alliance against the ability of everybody in the enemy alliance - Russian roulette without the real bullets - so unless your a gambler by nature AND can afford to loose the stakes there really is no point in using a wager.
Where possible use the lowest ranked vehicles you can when playing a wager, this will set you against other lower ranked vehicles. Many of those lower ranked vehicles will be owned by less experienced players than yourself and if you are in a 4 man squad that plays well as a team you can seriously improve your alliances chances of winning - but don't forget that others on in your alliance will also be less experienced than you and so nothing is guaranteed.
Happy hunting.
We did golden wagers with 4 man squad before and some times you win some times you lose.
Anyway make sure that the 4 man in your squad know what they are doing and are serieus and good players