So you think if John had accepted the extra $2000 to make the match happen back then they would have then gone to Danny and said "hey, John held out for an extra $2000 more than you did so even though you would have done it without the extra $2000 to be fair we are going to go ahead and give you an extra $2000 also so you are both getting the same amount"? I'm kind of doubting that. Like you said, it was only offered because John didn't want to play, and it took more $$ to convince him to. I'm sure they weren't going to pay it where they didn't have to (to Danny in that case). Not that there is anything wrong with that depending on your perspective, people get paid different amounts for the same services or goods all the time.
I think Danny's point is that if John was offered extra $ when he didn't want to play, but Danny isn't going to be offered the same thing when he doesn't want to play, then they are being treated very different. Again, happens all the time. I understand the sentiment though and it's a fair point. It is like when you coworker does the same job as you, has the same qualifications and does the same quality of work as you, but you find out they are earning a lot more than you are.
Of course it is always possible that Danny is actually willing to play for the $1000, and is just saying he doesn't want to play and holding out as an angle since he knows they were willing to pay extra in the past with John to make this very same match happen when he didn't want to play, and if they were willing to do it for John, then Danny is going to hold out for the same thing on principle and also to maximize his pay. And again, that happens all the time and depending on ones perspective there really isn't anything wrong with that either.
As I mentioned above though, all this holding out on principle, or not playing on pride, could backfire and cost a player a chance at a nice free payday, which even if it isn't as much as he would have wanted, is still pretty darn good and certainly better than he would otherwise likely to be earning in those same three days. Logic should be prevailing over pride and principle here though and they should both be jumping at the opportunity for free money. Offers like this don't just come along every day (or year, or decade...).