The sales people tell the owners best case numbers- like max range with one passenger at long range cruise from a sea level airport at ISA. Put a family onboard and take off out of ASE and you don't get nearly as far in many aircraft. I have also heard them just making stuff up at static demos and then gotten a good laugh when they were corrected by a real pilot. I have no idea what they tell them about the Hawker 400, but if they told them the whole truth then almost nobody would ever buy it with all it's limitations.