PHP json_decode arrays

Question

I use the following code

<?php 
$url = "https://www.example.com/price/x?get=json";
$json = file_get_contents($url);
$json = json_decode($json, true);
var_dump($json);
?>

The return is:

array(1) {    
           [0]=> array(2) 
               {               
                  [0]=> int(223450000) 
                  [1]=> float(831.54) 
               } 
         }

As I understand it, the arrays are not addressed, so I cannot address them directly. I want to output the array with the value 831.54 with echo. Does anyone have an idea how I can do this? Long searches and attempts have not helped me.