We don't know how bad you want to remain "friends?". We don't know why you would want to remain "friends?" with someone who does what he did? For a source of cattle that work for you, that are at a price that you find acceptable? Is the sale barn price acceptable as well? If you hadn't bought them, would they have been at the sale?
1. If he is an old man that is susceptible to forgetfulness or bad decisions (if you're getting over on an old man like that, lucky his boys don't find out), and/or you want to remain friends, then pay up. Or you take them back and get your check. Done. Adjust your future buying accordingly.
2. If he is an old codger trying to pull a fast one, and you don't care if you whiz him off or not - your call. Tell him to pound sand, come pick them up and bring the check you gave him and another for your time, fuel, and the grass they ate. Deal is a deal, if he wants to crawfish, he will have to pay the bs you can bill him for. Or go to small claims or whatever.
3. If you just want done with it, tell him come get them and bring your check, or you all figure what he would have paid for trucking/commission, subtract that off the $150, pay him, and call it even.
Only you know what will make you both happy, if anything. Be able to sleep at night. Don't do anything you wouldn't want your Granny to know about.
edit: Reading the above post you made, sounds like you better just pay him. I think that's the way you're leaning. And if you are cool with it, I sure am. Sounds like a wishy washy old man that is fun to talk to, not necessarily buy from though.