I think it's probable that a company can turn profits on quality works with sharealike licenses. Put simply, the assumption of the previous few centuries -- that the only real way to make a profit when publishing a work is by having a monopoly over the right to do so -- is incorrect.
I think the usual thought pattern is this: Letting people copy our work means people buy the copies instead of our version, so we lose those sales, so letting people copy our work is bad. That line of reasoning fails to engage any second-stage thinking.
People would create knock-offs, and some people would buy them instead of the Wizards products; that much is true. However, the losses wouldn't be that big, because competing with Wizards' quality and price (due to economy of scale) would be pretty hard.
The real benefit would be in increasing the player base. Some of us think $100 is too much to pay for D&D, so we don't buy, but we might pay half that much instead. If we did that (getting a knock-off), maybe we then introduce the game to new players, maybe players who can afford Wizards' more expensive version and have a mind to have nice hardcover original-source books.
Nevermind all the additional money they'd make from miniatures and other auxiliary products.
