I think the intent is really important though. I think you may not have to go extremely hard but make an offer he thinks is good enough that he won't get it on the market from a team he wants to play for. You might not say "hey this offer disappears in a week" but you might say here is what we think is fair... if its close lets figure it out. He may already (or should know what's out there) through back channels of course. If the offer doesn't materialize, like it sometimes doesn't, then you may be out a few million. He may also be able to dictate the length and options in that window so that it gives him some certainty and freedom later if its not great.
There is also the "I just want to get this done" factor to things.
I think we had an opportunity to get something in the realm of 25M a year done and maybe get all the favorable terms we want. I think if we come and say 5/125M or nothing this offseason... then he goes out and shops himself. Lakers certainly will offer him a deal in or above that... but we could just match. The real danger is Washington/BKN or another bottom feeder (maybe Charlotte if they clear one contract) making a 4/150-160 offer with less favorable terms. I don't think that happens but its not like a low likelihood.
Washington has like 80M in space or something ridiculous. What are they going to do with that? What young player or players do they think they can add? Sarr already famously sees himself as a 4 so maybe they go huge and make Walk an offer. They can still do everything else they want to do while they wait the couple days.
The more likely scenario is Indiana or LA want to acquire him through sign and trade and we get a first for playing along.