It's not really a cost thing... Nelson plugs aren't that expensive... It's more a matter of being able to pick up a plug whenever and where ever you want.
Nelson plugs can be had at [link=http://www.pspec.com/]Performance Specialties[/link] and [link=http://www.pacifier.com/~dcady/]Darrol Cady[/link], to name couple. They cost little over 3 bucks... like I said, it's not a cost thing.
If you don't mind ordering 10 or 20 plugs in advance, then by all means, stick with the Nelson plugs, as they offer slightly better performance compared to standard plugs. Jett advises the Nelson HD plug for the Q500 engine...