Prevent variable pricing options from being checked by default
<?php
/*
 * Plugin Name: Easy Digital Downloads - Price Option Not Checked
 * Description: Prevent variable pricing options from being checked by default
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

function sumobi_edd_price_option_checked( $checked, $download_id, $key ) {
	return '';
}
add_filter( 'edd_price_option_checked', 'sumobi_edd_price_option_checked', 10, 3 );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.