I use a couple pretty simple measures to get the technical debt idea across, with the numbers variable: "if we invest around 3 months now then we will reduce t

I use a couple pretty simple measures to get the technical debt idea across, with the numbers variable: "if we invest around 3 months now then we will reduce the time to market of every subsequent feature by about 2x and also decrease the number of bugs each feature produces by about 70%" Then make sure they understand that these are just approximate estimates, but it gets the idea and the urgency across.