PMPro Sponsored Members Example Variable seat pricing.

my_init_override_sponsored_members_pricing_update.php

<?php   // do not copy this line.
/**
 * Sponsored Members setup with child seat costs at checkout.
 *  SPONSOR SEAT + 4 seats 19.95 each
 * 		 + 5 to 19 @ 17.95 
 * 		 + 20 to 39 @ $15.95 
 * 		 + 40 to 79 @ 14.95
 * 
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

global $pmprosm_sponsored_account_levels;	
$pmprosm_sponsored_account_levels = array(	
	4 => array( //Sponsor Level
		'main_level_id' => 4, //Sponsor Level AGAIN
		'sponsored_level_id' => 5, //Child Level(s)
		'seat_cost' => 19.95, //cost per seat 4 and under
		'min_seats' => 4,
		'max_seats' => 79,
		'seat_cost_text' => '<br />(19.95 each) and then for child seats 5 to 20 @ 17.95 then child seats <br /> 21-40 @ $15.95 and seats 41-80 @ 14.95',
	)
);

/**
 * Remove Sponsored Members Pricing update and use our own.
 */
function my_init_override_sponsored_members_pricing_update() {
	remove_filter( 'pmpro_checkout_level', 'pmprosm_pmpro_checkout_levels' );
	add_filter( 'pmpro_checkout_level', 'my_custom_pmpro_seat_pricing' );
}
add_action( 'init', 'my_init_override_sponsored_members_pricing_update' );

/**
 * My custom pricing.
 */
function my_custom_pmpro_seat_pricing( $level ) {	
	// Only concerned about level 1
	if ( $level->id != 4 ) { // Change to Your Sponsor Level ID 
		return $level;
	}
	
	// get seats from submit
	if ( isset( $_REQUEST['seats'] ) )
		$seats = intval($_REQUEST['seats']);
	else
		$seats = "";
	
	switch ( $seats ) {
		case $seats < 5:
			$level->initial_payment = $level->initial_payment + ($seats * 19.95);
			$level->billing_amount = $level->billing_amount + ($seats * 19.95);
			break;
		case $seats <= 19:
			$level->initial_payment = $level->initial_payment + ($seats * 17.95) - 2;
			$level->billing_amount = $level->billing_amount + ($seats * 17.95) - 2;
		    break;	
        case $seats <= 39:
			$level->initial_payment = $level->initial_payment + ($seats * 15.95) - 4;
			$level->billing_amount = $level->billing_amount + ($seats * 15.95) - 4;
			break;
		case $seats <= 79:
			$level->initial_payment = $level->initial_payment + ($seats * 14.95) - 5;
			$level->billing_amount = $level->billing_amount + ($seats * 14.95) - 5;
			break;			
					
	}
		
	return $level;
}