Are iridium spark plugs worth the extra cost over copper?

For most modern engines, yes. Iridium and laser-iridium plugs in this list carry the longest service intervals and consistently strong verified-purchase ratings, which is why they command higher prices. Copper plugs like the NGK BR8ES and BPMR7A remain popular for small engines, motorcycles, and some performance applications where shorter intervals are acceptable and the lower price wins.