7 1/2 years of being a PhD student means 7 1/2 years of missed career growth, missed retirement funds, missed personal growth (how are you going to start a family in poverty-wages?). In the US postdocs are also counted as trainees (another scam) so people enter their careers in their late 30s, early 40s, with empty retirement accounts, no savings, and vaguely applicable skills. This might have been possible 20, 30 years ago, when OP's PI was training, but nowadays it's just a huge loss that isn't worth the vague scientific gains.