First of all, SF4 is basically a new game. It’s not just a rehashed HD version, it’s a new game, with new models, new coding, new graphics, new physics, and a ton of new expenses. It wasn’t as cheap as you think it was to develop.
MadCatz made the peripherals, not Capcom, so no, there wasn’t too much to gain off controllers and such.
Arcade units cost thousands of dollars to produce and sell. Which barely any arcades exist in the USA and if they do, not all have SF4 cabinets.
Not everyone purchased the costumes.
And yes, I believe another Resident Evil game will bring in a lot of money, as RE1-5 have, why not 6? They keep making them, and they keep selling well.
SF4, which sold good, did not sell great. There is a strong culture and following, as is shown by these forums, but this isn’t anything compared to the main stream gamers that would purchase RE games over SF4. How do I know this? Look at the sales charts.
So yes, basic economics, overall sales of SF4 are diminutive than RE sales, so this is why (I could be wrong) that Capcom would consider not following up with another SF4 game, compared to creating a new RE game.
But to remind you, I am not against you, I actually purchased SF4 and not RE. My theory just makes more sense to yours.