<?php                                                                           
                                                                                
$array = array(                                                                 
    array(2 => 50000),                                                          
    array(2 => 30000),                                                          
    array(1 => 25000),                                                          
    array(1 => 20000),                                                          
    array(1 => 10000),                                                          
);                                                                              
                                                                                
$flat_array = array_map('current', $array);                                     
                                                                                
print_r($flat_array);                                                           

Array
(
    [0] => 50000
    [1] => 30000
    [2] => 25000
    [3] => 20000
    [4] => 10000
)