The numbers you are looking for are constantly changing (dynamic). Currently:
Bronze win: +6
Bronze loss: -10
Silver win: +9
Silver loss: -20
Gold win: +6
Gold loss: -30
Platinum win: +15
Platinum loss: -40
But in a few hours those numbers might change again. They have to change to keep new decks close to rank #250, the more decks are submitted, the higher the competition for the top 250 positions, the lower the rating gained per win.
With constant numbers two bad things would eventually happen:
Bad thing #1: rating gain is too high and new decks enter at rankings >500 and they do not even get a chance to compete
Bad thing #2: rating gain is too low and all decks in the league have a negative score, new decks enter as rank#1
Therefore those numbers will keep fluctuating to maintain the balance, that means that sometime the gain in rating for 1 win is much smaller than the loss of rating, but if in a league there are 1,500 decks submitted (silver,gold) and only the top500 is in the game, only the best decks (top 250, 17%) get positive score.
In other words, the competition for bronze, silver and gold is very bad at the moment, the only way out is to get in platinum league, only about 400 decks there.