It can depend on the market.
Both renditions of my Mercy are based in Seoul. For South Korean domestic routes, the extra speed of the CRJ is negligible, and not worth the additional costs incurred. And for Chinese and Japanese routes, on most major markets, it makes far more sense to send in a larger plane (F100, MD80, 737, or A320) due to higher demands. As for long, lean markets (say, southern China, or outlying Japanese places like Okinawa or Sendai), the basic CRJs struggle to break even. And that was with the lower 1998 fuel prices (it was the old game where fuel prices were historical).
There is a reason why in real life, no South Korean airline flies regional jets. Though I do find it stupid that both Korean Air and Asiana run all-jet domestic services - it IS well known that they are sustained only via artificially high fares. All South Korean domestic runs are short enough that a 737 or an A320 will barely hit 26,000 feet cruising altitude, and only for a few minutes tops. A jet is simply not designed for short hops like that. The low-cost competitors do fly props, which work a lot better.
There are some markets (probably western US) where the basic CRJ will make good sense. Not for me, though, as long as I'm in Seoul. It's either the CRJ-900, the E170/190, or the smallest variants of larger planes (737-600 or A318).