Andrew,
(I have no association with Moz)
With MozLocal you're getting distribution to the top 4 data aggregators with one simple submission. I know if you go direct to just one (like Neustar/Localeze) they can charge you yearly and it's MUCH more expensive than Moz just for this one site. So it's still a good deal. Last time I checked it was like $300/yr. per location just for Neustar/Localeze.
Also, submitting to these services more than once is important. It shows downstream that you're still an active business and the sites can use resubmission as a positive signal to keep you in their listings.
I've done a lot of research and I've submitted to these services individually before. I've even paid to be a partner member with Neustar to distribute listings and MozLocal is the best and easiest way to distribute to the big four (and it will hopefully only get better with age.)
Well worth the cost in my opinion.