Besides the high quality and higher thermal insulation that Eric mentioned, the convolute liners which others and myself sell are manufactured in a completely different method than what spiral tubes are. Convolute wound tubes are MUCH more labor intensive and use more expensive materials, so manufacturing differences are the main driving force in the cost difference.
Once the setup is done, spiral tube machines can run continuously, making tube after tube on the same mandrel until the giant rolls of paper run out. Even then, adding a new roll is a fairly easy process. The kraft paper they are made from has been impregnated with phenolic resin. Once the tubes are made, they are baked, and then they are pretty much done.
Convolute wound tubes are made one at a time and each tube is wrapped on its own chrome plated mandrel. The substrate is ran through a bath of resin, ran through a squeegee (more or less) to remove excess resin and then wrapped around an individual chrome plated mandrel. Until the tube is wrapped, baked, cured and centerless ground to its final OD, and then removed from the mandrel, the mandrel can not be used to make another tube. So if you want to make lots of tubes in a short period of time and in many different sizes, you need a BOAT LOAD of expensive mandrels.
From a thermal stand point, convolute tubes have roughly about 50-55% phenolic resin in them vs only around 5~20% in spiral tubes. Phenolic resin is what mainly does most of the insulating. The substrate alone would just burn into ash and float away. Phenolic however chars and remains in place. A higher phenolic resin content is the main reason why they are far superior thermal insulators. The stiffer and more rigid the spiral phenolic tubes are, the more phenolic resin content. The softer and less brittle they are, the less phenolic resin. Convolute paper grades like X, XX, and XXX are slightly more dense (flat paper) than LE or CE grades (woven fabrics) and thus have slightly better insulating properties. In a nut shell, you get what you pay for, but each has its place for use.