I don't think this is entirely fair. There is a lot of free preview stuff WotC posts, both at the start of the month when showing upcoming products, and numerous individual previews for each book over the course of the month leading up to release. Plus, lately, a lot of free excerpts shared with various RPG blogs as well as on Facebook, Twitter, etc. Plus the demo of the character builder and the compendium, both of which have a lot of free info for early levels of play. Plus the early issues of the online magazines which remain free, plus H1 which is available online for free.
I honestly can't make any actual comparisons to other companies (since I haven't seen firsthand what Paizo or others make available), but I think the claim that the only way to look at 4E material is to go behind the paywall of DDI... is simply wrong, and has no basis in actual reality.