As an intermediary, I have met sellers who feel they have the wherewithal to complete a business transaction without the aide of an intermediary or advisor, and while the advisor does have a success fee, this fee creates a mutual interest for both parties; to receive as much compensation from the buyer as possible.
More importantly many small and mid–market companies do not have the experience, knowledge and resources to quarterback a merger or acquisition, and the cost of learning is high, and can even be to the detriment of the business and the seller.
Advisors and intermediaries will have experience in deal making while still maintaining a fiduciary responsibility to their client.
Further advisors know how to spot opportunities in a transaction to maximize long term value, such as with a rollover, which is not necessarily going to be something the seller would be aware to look or ask for in a transaction.
Sellers should not step over a dollar to save a dime in such a vital transaction, and should absolutely listen to an advisor or intermediary to guide them through this new and uncertain process.