Maybe so, but only if the dealer is doing such deals continuously. What is earned on such a deal has to cover the time when admin is being done. Tax returns, dealing with distributors, tyre kickers or those times when customers are short on the ground etc, etc all take time and that time is not generating income. That’s before considering cost of premises and staff.
Obviously a hobbyist dealer, working from home and not dependant on the income to live has more scope for undercutting the market and some of them have a reputation for threatening the more established dealers, whom we will doubtless miss when they are gone and the hobbyist dealer moves on to a new hobby.
When it comes to doing a deal there is often a range of flexibility, both for buyer and seller, and if those ranges overlap then business can be done and a good working relationship developed. If the ranges don’t overlap then no deal.