In my estimation that would be an expensive way to do business.
Give him a $1M raise to hold over a couple years, before everyone else notices or be forced to give him $2+M, after everyone realizes and comes with their (bigger) checkbooks.
I wrote in another thread that it is almost always cheaper (in my experience) to overpay talent early by 15-20% than to underpay by 15-20%. That may seem counterintutitive in the short term, but here are a few (not exhaustive) reasons I believe it saves money in the long term.
1. Replacing (equal) talent is almost always more expensive than retianing it. (eg, Paying a premium to bring someone from another shop beacuse happy productive employees do not undergo the stress of moving jobs for a lateral comp situation. Plus the actual search $ cost and time cost spent looking for replacement instead of working on your business, other related costs etc)
2. Drop in productivity/revenues of your buiness while you undergo the transition. New systems, managers, sales talent almost always take a period of time before they have their respective businesses running close to optimum/steady state. If you save $1-2M in expenses but it costs you $3-5M in sales, that is not a good trade.
3. Many studies show that *on average* increased compensation results in more productivity from workers due to their increased sense of responsibility to earn what they are paid. Also their is increased urgency to retain their current position since a similar role/responsibility may not exist for them at this current comp so they are highly motivated to maintain their current (unique) circumstance.
EDIT: #3 is less relevant to head coaches but applies more to staff.