Dr Teo, who was made a Member of the Order of Australia this week, sold off the tickets at a charity auction in October.
Sydney University public health professor Simon Chapman was at the auction and says selling the tickets was unethical, even if the patient has given consent.
"If you're a patient who is undergoing a very serious procedure such as brain surgery for cancer, and you're in the hands - if you like - of a leading surgeon and the surgeon makes that request of you, there is an inherent power imbalance there," he said.
"Yes, you can consent. You can say, 'Yes that's fine'. But what if you had reservations?
"What if you didn't want your privacy invaded like that. Would you really be able to say 'No, look I'd rather not'?
"You probably would think twice about saying no."
Dr Teo says that is not an issue because he develops strong friendships with his patients, but Professor Chapman says bioethics is not down to the person making the call.
"There are standards, there are arguments, there are ethical principles which need to be considered in the cool light of day," he said.
The Royal Australasian College of Surgeons will investigate whether Dr Teo or the hospital breached ethical guidelines.
The college's executive director of surgical affairs, Dr John Quinn, says watching surgery for a price is unacceptable.
"Surgery is not a spectator sport. It is a really quite a serious activity and often a life or death situation, and viewing live surgery is not regarded as appropriate behaviour.
"The college doesn't have any authority over hospitals. The public hospitals are under the direction, guidance and control of the health departments in the various states.
"The college does have a code of conduct which all fellows and trainees in surgery of the College of Surgeons are expected to abide."
In an interview with 702 ABC Sydney, Dr Teo acknowledged the concerns, but said the key consideration was the motive of the surgeon involved.
"It would be terrible if someone offered this item and patient care were to be compromised," he said.
He said he tried to avoid any negative impact on patients through hospital protocols to prevent infection, but also through his own rules.
"I would never approach the patient myself. I think that puts them in an awkward situation," he said.
"I make sure someone else approaches them for their consent so they can easily say no, and thankfully we've had patients say no."
Dr Teo said he auctioned the tickets to create awareness.
"The reason I do it is for the greater good of the community," he said.
"To try and get more money into research. To try and tell people brain cancer is not just a name or a disease.
"I think this personal experience allows people to see that cancer affects you and me."