Again, your numbers appear off, and the numbers have changed very recently so the duration of talks is irrelevant.
From memory (and all this is going off various reports on here, and without knowledge of how much is cap salary/TPA)
Our initial offer (before the salary cap was known) was about 1.25 million, Parra were at 1.05-1.1 mil, so the difference then was roughly 600k over the course of the contract. Not huge given the result of the two sides, we need to offer way more just to have a chance.
Now that the cap is sorted and contracts have risen due to relevant clauses, Moses is already on over a million this season, so all subsequent offers are now rising accordingly. Ours from 1.25mil to perhaps 1.4, Parra will likely have upped their offer to 1.2-1.25 mil. This would have only happened last week, and again the difference over the course of the contract is only 600k, maybe 750k. Considerable difference, but you're comparing 4 years with the spooner to with a grand finalist.
Reports from the parra forum that we've now known gone to 1.5 million, which if so, is probably necessary to increase the gap between our offer and Parra's by a sufficient margin to overlook recent performance. Will they again increase their bid or will they stop negotiating? Once this is known there should be a decision quick smart. If our offer is 4x1.5mil then that's 6million, a bit less if the 1.5 figure is part of a back-ended deal moving from 1.4-1.5. The likelihood is there's now well over a million between our offer and Parra's enough to cause serious deliberation. It shows how much we value him, which is great for his significant ego. But will the lure of more likely short term success render the cash as less significant?