The exchange rate between Google Play cards and the Nigerian Naira can fluctuate daily. To determine how much 15 Google Play cards are worth in Naira today, one needs to consider various factors.

Firstly, exchange rates are influenced by the global economic situation. If there is instability in the international markets, it can cause the value of the Naira to either increase or decrease relative to the Google Play card value. Financial trends and geopolitical events also play a significant role.
Secondly, the availability of currency exchange services affects the conversion. Different platforms may offer slightly different rates. Some may have better rates due to their economies of scale or relationships with financial institutions.
Finally, it's crucial to check reliable financial sources or currency exchange platforms to get the most accurate conversion rate for today. These sources are updated regularly to reflect the current market conditions. Without the specific rate at the moment, it's difficult to precisely state how much 15 Google Play cards are equivalent to in Naira today. However, by following these steps and keeping an eye on the relevant factors, one can obtain a relatively accurate figure.