Buy a Ios or Google Play Card

Afaik not. There are often discounts for IOS cards (mostly at retailers), but Play Store is rare. Might also be regional.

The google play cards are region locked ( mostly ) and the sites who seem to sell stuff cheaper then its value seem to be shady at best ...

Friend got me one from here

They are all region locked but you can bypass that by changing your country in Gmail settings to a country where the card was purchased it. Remember to use up any remaining funds you have on play store since the country change will reset your whole credit. Also, the currency will then be converted to the currency of where the card was from but that doesn't matter much.