Actually, with a little digging this is quite easy to do. WooCommerce has already set up a filter so all you have to do it add a small snippet in your functions.php file.
// Modify the default WooCommerce orderby dropdown
//
// Options: menu_order, popularity, rating, date, price, price-desc
function my_woocommerce_catalog_orderby( $orderby ) {
unset($orderby["price"]);
unset($orderby["price-desc"]);
return $orderby;
}
add_filter( "woocommerce_catalog_orderby", "my_woocommerce_catalog_orderby", 20 );
taken from: https://gist.github.com/BFTrick/5806726
In this example I’m removing price
& price-desc
but you can remove any of the options