Advertisers always go with the time slot winners when they can. There is/was NO sign of advertisers pulling out.

Plus, a large night talk show doesn't have tge kind of production costs of any kind of scripted TV show with multiple sets, actors, script writers, overhead, etc. Costs were stable. Guests weren't paid. No extra sets to build. So it doesn't ring true whatsoever!

AND... The show continues for another YEAR after its cancelation! Further cementing the silliness of costs being the reason.