It's really a tough call because there's two legit ways to look at negotiating his contract.
Watson and his camp are going to point out that *when he plays* his impact on the offense and his product are elite, among the best in the league. PFF, for instance, had him graded out as the 6th-best WR in the league last season. He's 2nd in the league in yards per rec, and 3rd in "deep receptions" (yards the ball has to travel before the catch) and ADOT.
In terms of AAV, the 6th-highest paid WR in the league right now is currently earning about 32m/yr (DK Metcalf/Garrett Wilson).
Meanwhile from the team's perspective they will probably emphasize his injury history, availability concerns, and the lack of "raw" production vs per-snap production. For instance Watson is 120th in receptions, 58th in rec yards, 38th in TD, 38th in EPA, and 17th in yards per game and 18th in rec success percentage. Whatever "rank" you pick from those corresponds to a much, MUCH lower salary.
It's also worth noting where the "floor" here is though. Currently, an "above average" WR is going to make 25m/yr AAV. Period. If you are in the top 16 WRs in the league, that's your minimum. Even 30m is basically "top 10 money" at this point. Watson is 100% going to get top-half money and in all likelihood he will be pushing that top-10 pay as well IMO. I can understand some trepidation about wanting to make him a top-10 paid WR but much worse than that is just dreaming at this point.