jQuery('select[name*=product_type_id]').each(function() {
  console.log(jQuery(this).val());
  // these categories won't have products associated to them
  // MAKE SURE the ids stay the same
  if ( jQuery.inArray(jQuery(this).val(), ["4", "6", "7"]) )
    // hide the product_id select parent, p in this case
    jQuery(this).parent().next().hide();
});

// NOTE TO SELF
// SLOW THE FUCK DOWN! RTFM. RTFM AGAIN. AND AGAIN.