"Our buyer has spent $2.5m on DD so far."
If you're exiting, the buyer's DD spend is a very safe sign of skin in the game. At $2.5m, heads will roll if the deal doesn't close.
As a seller, you want to get your buyer as pregnant as possible. So, push them to start & spend $ on DD, particularly legal. A good sell-side banker will be on top of this.