[Warning: rambling philosophical post]
My approach with car purchases is this: given a decorated model with road number, I go search for that number series in the online proto-photo archives (this is where modeling modern pays off) and see if it's a decent match according to my threshold du jour. If it's close enough (and the model is decent quality, and I have money) I buy it. For this BNSF gon, it only took a few minutes.
Another example was the Athearn CSX 52' gon. In that case, the number series Athearn used did not match the proto car, but another proto number series did match pretty well, so I bought it, despite Athearn's poor research. If I feel ambitious, I'll renumber it, but I'll probably just lower it, weather it and call it a day.
My threshold is higher for locos and intermodel. Still waiting for those 4000-series BNSF Dash-9s...
