Powerful things to sell books?

[Tiktakkat]

Do you think WotC puts powerful things in Splat books to help sell them?

For example the new races from Ro* are all kinda powerful (if not always up to human/ strongheart halfling standards)

It is a bit more complex than that, but basically, yes.

First, there is the competition among most authors to make their thing (race, class, country, whatever) "cooler" than the thing the other authors are writing. That primarily translates as throwing more power at them.

Second, is untested synergy. The more stuff you add from a greater pool of authors who are not in constant contact, cross-referencing everything they write, the greater the chance, approaching 100%, that you get synergies between various basic elements (races, classes, feats, spells, and equipment) that produce results disproportionately powerful and thus destructive to the overall game balance.

Third, is basic power creep. Any time you look to expand the options in a game, you have to do something to make them attractive. This almost always translates as making them just a little bit more powerful than previous options.

Fourth, is raw giveaway. For the same reason it was decided that all books need crunch (meaning actual rules material), even the most basic background book, to drive sales, it is often decided that said crunch be more powerful than previous material to entice potential customers to "pay to play" "better" (meaning just more powerful) characters than anybody who does not purchase the new hotness.

The first two can be controlled by a good enough product line editor, as even the best authors give in to the temptation. (They just have the integrity to admit it.)
The third by a decent brand manager, who hires the right authors and editors in the first place.
The last is a corporate level decision, and thus the most difficult to control, or reverse once it begins. It is the game equivalent of jumping the shark.