I think the price difference you see is from materials, construction, and extras.
The Paris is a simple polyethylene thermomold with no frills. Ok, so Hamtero didn't take his, but I do have a friend who built Ed's Paris with fiberglass poles setup, shipped it for his Denali trip, and left it there. He has some good pictures on the sidehills where his sled (with fins) stayed on track while everyone in front had sleds sliding downhill.
The composite ones are handmade and working with fiberglass is a lot more tedious - I'm just saying from personal experience patching up my kayak. Also, from experience in the kayak fiberglass is pretty abrasion resistant and won't gouge deeply, but gel coatings can crack and so can the fiberglass. My guess as to why the pulks are not 100% fiberglass is that the poly probably helps the pulk keep it's shape and ads cheaper reinforcement - fiberglass is strong, but can have a lot of flex, which can be reinforced by thickening the material - you could add more fiberglass, but it seems like they chose to mix the two to get that extra durability and redundancy from having two different materials... and it ends up being cheaper.
Again, from the book of kayaking and materials- poly scratches easier, but it pretty durable on impact since it bounces off instead of wanting to crack. Fiberglass doesn't gouge as easily (so it will cause less drag over snow over time) and is easier to repair, but can crack. Kevlar is the light standard but very expensive and harder to repair.
And of course there are the obvious extras like the built in straps and covers in the more expensive ones.
Also a note on the Mad River Rocket from our Baxter trip last year - most of us had the Paris and two had the MRR. It was fine on the way out when the surface was icy, but on the way in to Roaring Brook and then to Chimney Pond, with the 1'+ of snow we got, the tubby shape of the Rocket caused a lot of drag in the deep snow where the Paris sleds seemed to ride on top of it much better.
What I learned about poles I posted here:
http://vftt.org/forums/showthread.php?t=9711&highlight=poles&page=3