1x, the exact same as a pokeball
The Love Ball (ラブラブボール Love Love Ball) should be used on a Pokémon of the same species and opposite gender as the player's Pokémon
This means that Love Ball will only work if the wild Pokemon is of the SAME Species - so that means, you're using a charmander, the other Pokemon must also be a charmander, of the opposite gender for the 8x effect of love ball to take affect. Since obviously you weren't meeting another Palkia in the wild, and also because Palkia is genderless, Love Ball was being a Poke Ball.
So indeed it was luck, like it or not. I once caught a Mewtwo in HeartGold with a Friend Ball after throwing about 50 assorted balls including dusk and ultra balls.. so luck, ftw!