I used to have guys come in all the time and do this. Some bought cars, but not always for a good deal. The ones who didn’t either felt that we should sell them cars for less than our cost, or (amusingly) failed to realize that the websites they were researching (yes, even the big ones) got things wrong. I had one guy shove a paper with his expectations in my face, and when I told him I couldn’t do it he stormed off before I could even say “because they don’t make them in this configuration!” I’m hoping he eventually figured that out, but he wasted a lot of effort in the process!