before people keep posting out of panic from the title, just know that, again, his price hasn't gone up at all because of todays signings. things are the same with Mac as they were a couple days ago. nothing has changed. relax.
I don't know exactly how arbitration works, but I'm sure that the arbitrators are aware that there's a difference between UFAs, where the whole league can get into a bidding war, and RFAs, where it's the team and the player (barring the rare offer-sheet). Perhaps the overall trend of contracts will make his go up, but I don't see him getting more than about $3 million, if that. People should remember that the only reason he was awarded $2.4M last year was that Atlanta didn't put in any counteroffer, knowing they were going to let him go anyway.
What this has done though is make me want him re-signed. I thought perhaps we could get a replacement if we don't agree with the arbitrator's results, but with the huge contracts free agents received, I'd easily take MacArthur over any of the players mentioned in the OP or leftover now, even if it's a bit higher than we expected a few weeks ago.