Give users bonus points when they buy points using the buyCRED add-on. Base the amount of bonus a user gets on their current rank.

mycred-run-this-filter-example3

/**
 * Bonus Points
 * Give users bonus points when they buy points using buyCRED
 * based on their rank. Required us to know the Rank post ID for comparisons.
 * @version 1.0
 */
function mycred_pro_buycred_bonus( $run_this, $mycred ) {

	// Only applicable for point purchases via buyCRED and if the Ranks add-on is enabled
	if ( substr( $run_this['ref'], 0, 15 ) != 'buy_creds_with_' || ! function_exists( 'mycred_get_users_rank_id' ) ) return $run_this;

	extract( $run_this );

	// Get the users current rank post ID
	$users_rank_id = mycred_get_users_rank_id( $user_id, $type );

	// Example: Newbee rank post ID 10
	// If user has this rank, give the user 10 points more
	if ( $users_rank_id == 10 )
		$run_this['amount'] = $amount + 10;

	// Example: Master rank post ID 12
	// If user has this rank, give the user 100 points more
	elseif ( $users_rank_id == 12 )
		$run_this['amount'] = $amount + 100;

	return $run_this;

}
add_filter( 'mycred_run_this', 'mycred_pro_buycred_bonus', 10, 2 );