Actually, that was true until this year. This year the Focus got unified. If you don't believe me, go take a look. The dealer near me has an RS on the showroom floor, too (and oh my is it pretty). A SEL or Titanium Focus is in the mid to upper $20K range, and is aimed squarely at the GTI and Mazda Speed3 (which yes, was always a euro spec focus, for the most part). But the ST which is coming out in the near future will be aimed somewhere between the WRX and the STi, but at a much lower price point (low to mid $20K range). The RS, which admittedly is exceedingly hard to find, is priced comparably to the STi, and at least keeps up with it. It just depends on what you want in a rally car.
But you're right, until recently that wasn't true.