Question Author
Gromit: "Opinions do not become valid by investing money in them. " - no but it indicats the confidence of the opinion holder in their own view
"Your opinion is no better than mine because you are willing to gamble money on them. " - It's not gambling if you are confident of your opinion, I am, to me it's not gambling.
Do not focus on the "bet" as a gamble more a measure of your confidence in your own opinion. How can you expect to win an argument when you don't even believe your own view enough to back it?