Understand that ANY product has a "side" price tag, paid by granting options or "payment for expenses" to the senior individual. Another way to look at that. Ask ANY member of your board of advisors to disclose ANY conflict of interest.
If StartUp sells product/services/SaaS to BigCo. then BigCo. "advisor" should disclose ANY payment, direct or indirect, travel or non-travel, and ANY stock options.
This is what had to be done with the large drug companies, forcing them to disclose payments to providers/medical doctors who had the authority to buy drugs. Full disclosure + penalties for lack of disclosure ---> that was the end for the drug sales rep who were doling "educational conference tickets, all expenses paid for you and your spouse, ALL expenses paid, and of course compensation for your time". Of course said conference had to happen in Tahiti, San Francisco, Seychelles, etc...