Change the Out of stock string based on the product's cost

functions.php

<?php
add_filter( 'woocommerce_get_availability_text', 'price_out_of_stock_string', 10, 2 );
function price_out_of_stock_string( $text, $product ) {
    if ( $text === 'Out of stock' && $product->get_price() < 100 ) {
	    return "Out of stock because of The Queen's Gambit";
	}

	return $text;
}