Change subscription price.

functions.php

<?php

function update_subscription_with_original_price( $subscription_id, $args ) {
    global $wpdb;

    // Get the download ID from the $args array
    $download_id = $args['product_id'];

    // Get the price ID if variable pricing is used
    $price_id = ! empty( $args['price_id'] ) ? $args['price_id'] : null;

    // Get the original price based on the price ID
    if ( $price_id ) {
        $original_price = edd_get_price_option_amount( $download_id, $price_id );
    } else {
        $original_price = edd_get_download_price( $download_id );
    }

$discounted_price = $original_price - ($original_price * (25/100));

    // Update the subscription's recurring amount directly in the database
    $wpdb->update(
        $wpdb->prefix . 'edd_subscriptions',
        array( 'recurring_amount' => $discounted_price ),
        array( 'id' => $subscription_id ),
        array( '%f' ), // Data type for recurring_amount
        array( '%d' )  // Data type for subscription ID
    );
}
add_action( 'edd_subscription_post_create', 'update_subscription_with_original_price', 10, 2 );