Sets a purchase amount and prevents customers from purchasing more than that amount at one time.
<?php
/*
 * Plugin Name: Easy Digital Downloads - Limit Purchase Total
 * Description: Sets a purchase amount and prevents customers from purchasing more than that amount at one time.
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

function pw_edd_limit_total_purchase( $valid_data, $post_data ) {
	
	if( edd_get_cart_total() > 100 ) {
		edd_set_error( 'too_much', 'You cannot purchase that much at one time.' );
	}

}
add_action( 'edd_checkout_error_checks', 'pw_edd_limit_total_purchase' );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.