I do have stats, actually...
2023: 2 (Scherzer and Verlander, who said he'd only waive his NTC for one team, the Astros)
2022: 0
2021: 1 (Scherzer again)
2020: 0
2019: 0
And this doesn't even include all of the deals that were nixed because of a NTC and or are never even pursued because of the presence of a NTC. Bottom line: it's rare.
As for Yelich's $26 million, it's definitely less than 1/4 or 1/5 of the payroll. Furthermore, it's an opportunity cost-type situation. If the Brewers traded Yelich to rid themselves of his contract, they'd still have to find a way to replace his production, which this year was worth 4.1 fWAR, second best on the team. The cost for that sort of production would be at least $20 million if they tried to plug the resulting hole in FA, in which case they'd save very little to no money to upgrade the rest of the roster. We have young OF talent that we could go to instead, but that's still asking a lot for them to replicate Yelich's production and could ultimately negate any upgrades made to the rest of the roster due to the cost savings from a trade.
Moreover, the Brewers would almost certainly have to eat a significant portion of Yelich's salary in any trade.
As I've been saying, the incentive is relatively low for the Brewers to trade Yelich at this point and his possession of a full NTC renders it improbable to where there's little point in discussing it.