Regarding the outed Bugatti:
The bike is strictly a dolled up gas-pipe frame, as a complete bike it is undoubtedly worth less than the parts. So to assign a value I would suggest that it is only worth as much as the parts minus the work needed to take them off.
Ettore Bugatti was Italian and did indeed undergo his apprenticeship in the bicycle business, at Prinetti & Stucchi. Being an eclectic designer, he may have built a few bikes here and there, but this was never a major part of his company's industrial production.
The family name Bugatti is quite common in Italy, so it is not at all unusual to have somebody by that name give it to a line of bikes made for them. In my eyes, the auction bike looks very similar to some Garlatti bikes that I have seen.