I would pay 700-800 for a set. But for that price, I would want it to be prototypical. TTUX and B&O would be 2 different eras. An early second generation diesel would be the newest locomotive that would be appropriate. TTUX and a SD70, the trailers/containers would have to be contemporary. There is a price point where I would abandon an offering if it was fantasy.
Don't mean to rain on anyone's parade, I do support the LCCA's UP Baldwin set even though the locomotive should not have the flag paint scheme on it. It should have the slogans "Route of the Streamliners," or "Serves the West" on the hood or cab sides. Even though no Baldwin may have worn a slogan, at least it is era sensitive to the model. But I intend to buy the set anyway because I welcome another Flyer set promoted from another source. However if the set is going to go upscale, I'd need authenticity to pull the trigger.
Sorry, I guess I am just no fun. But flirting with a grand price tag, it has to be worth it to me.
Here is a quick image I found on the web of an Athearn HO EMD SW that illustrates the slogan. Sorry, it loaded twice.