I was going to say 28k isn't necessarily better before I read your second paragraph, but that's the key, the negotiated price doesn't mean a lot, as this alone does not quantify its value.
If you pay more but get it sooner, then great, good call as the benefit may outweigh any cost (this is where we were at)
If you pay more but get it sooner until some other buyers appear, then it's a good call whilst you've beat everyone else, but then develops into poorer value (this is probably where we're at now)
I don't for one second think that there would be a clause that we got every dose first, as no supplier in their right mind would ever agree to this, nobody would even ask for it as they would get laughed out of the door.
Anyone that thinks "we got our order in first, we should get our goods first, the rest should wait" needs to spend some time on negotiating contracts, as it's not the same as ordering a pizza.