OK, so put yourself in the coaches shoes. You want college coaches to rely on your assessment of players so that when you recommend a player, the college coaches take the recommendation seriously. That benefits your players over time as more college coaches rely on you for input about players.
If you talk up and recommend marginal players, college coaches will stop paying attention to you. And in the real world, most of your players are marginal and you know it.
So you get a call from a coach, asking about a player on your team. You have to give him the honest assessment. In the OP situation, the coach proably told him good things about the player but if being honest, he didn't say that he is the best player to come along in quite a while. Based on the college coach coming back with an offer, one has to assume that the coach gave a pretty good,accurate assessment and didn't give negative feedback (if he gave negative feedback there would have been no offer).
And in the conversation the college coach probably asks if there are any other players on the team they should be contacting. Since the OP acknowledged that their player is not the best, but in the top 5 and the coach knows the college coach likes the original player, shouldn't the coach suggest taking a look at the other 4 top players on the team?
If you were the parents of those other four players, wouldn't you expect the coach to promote your players?
Tough situation for the coach. I would hope that the coach would promote all of his players who he thinks have the talent to play at that level. Be honest and make sure that the college coach will want your opinion in future situations.
At the same time, I would expect that the coach would talk to the player and parents about any conversations he has had with college coaches and keep them all in the loop. Tell the OP what he shared with the college coach about your player - doesn't need to tell you what he told the college coach about someone else's child.
But be realistic, a player who gets serious money and is only one of the top 5 on their team must 1) either be on a national championship caliber team or 2) the coach has done a tremendous job getting exposure and promoting his players. It is rare that even the top player on mediocre teams get serious money.
IMO you should thank the coach for helping to get your child some money in a very competitive environment. Expecting top dollars for a good, but not great, player is somewhat unrealistic.