DCC RPG will be printed on 70# uncoated offset. That is a durable, heavyweight paper stock near the upper end of what most printers keep in stock. It is not the "slick" type paper that you see used in color products; it is a more textured paper. When you read RPG products that feel like they are on flimsy paper, that is typically 50# stock (which I don't use). The real test is whether you can see the blacks through the page - i.e. is a dark illustration visible on the other side of the page. With 50# paper, it is; with 70#, it is not.
As long as we are on the subject - I am also using Smythe-sewn binding. That means nothing to most people but it is the difference between a heavily-referenced RPG falling apart at the binding or not. Smythe-sewn features an adhesive binding AND sewn threads to hold the binding together. All those RPG's you bought that fell apart after a couple months of use...well, they used adhesive only. Smythe-sewn is more expensive but it is worth it.