The comments about "thickness" are correct, when compared to what the cars originally came with. From about 1980 and later, the supplied vinyls had all of the correct outer looks, colors, and grains of the original tops, but that's where things got different.
I was at a trim shop in the later '70s where a customer was getting the top on their '74 Charger replaced. I asked the worker there about the car, as the top didn't look that "bad" to me. He then stated that they were lucky enough to find some of the original yardage for the job (no mention of where). THEN he showed me the difference in what they got and what was generally available. What was generally available (at that time) was termed "gauze back". When he put the two vinyls side by side, the differences were graphic. The vinyl "build" on top of the backing (thick-back) was much thicker, by approximately 40%. The backing actually looked like "gauze" when compared to the thick and more substantial "twill-style" back of the OEM vinyl. Once on the car, the gauze-back top would look like it should, so all of the differences in build thickness would not be known.
Several years later, at Mopar Nats, some "in the box factory original vinyl tops" were selling for about $500.00. When I saw the edge of one, it was the thick-back vinyl. Only thing that concerned me was that the vinyl was neatly folder and slid into a box. Obviously having been that way for many years, which might make getting them flattened out for instalation more of an issue than with a new-production item. Most of what they had was B-body tops.
I believe that everything past about 1973 model year (after which Chrysler seemed to use "GM grain" vinyls on the newer platforms, which was readily-available, but maintained the boar grain for the B-body cars for '74), everythng was the gauze-back product. Probably as all of the correct-grain Chrysler products tops are now, I suspect.
Considering that Newstalgia's vinyl top materials look to be GM-oriented, that migth be one reason their prices are less than places like YearONE and similar. A wider market for more sales using products that were widely-available, then and now. Whereas YearONE and similar will have a more focused market for those who expect what they purchase to be correct for their vehicle, by observation.
One thing about YearONE, in the middle '80s or so, was that the more you bought from them, the more volume discounts you could get, from their stated pricing. Sometimes, even better than their "designated dealers" could get the same things for. As happened to a couple of our Mopar club members discovered (one a designated dealer/broker and the other one who was doing a Superbird and had other friends who needed things for their non-Mopar vehicles).
I realize that price is important, but getting correct items can be variable in importance, generally.
Enjoy!
CBODY67