Based on the official website, it is a breakdown of how much PR you get for the prepaid cards available in Mexico.
$ 200 MXN = 1920 RP
How do I redeem my card?
1. Open the League of Legends client or visit the LOL SIGN UP page to create an account.
2. Click on the button of the Store .
3. Click on the Buy RP button .
4. Select the Prepaid Cards and enter the code.
5. Click Send . Your Riot Points have been added to your account!