Limiting your analysis to “coastal cities” is where I think you go astray. I grew up in the DC suburbs, in Northern Virginia, in a 3BR, 1,100 square foot house that my parents bought for $175,000 ($350,000 adjusted for inflation). Today, that same house is almost $700,000. My parents couldn’t have afforded to buy it today. But it’s also a totally different kind of town. Back in the early 1990s, the town I grew up in was squarely middle class, devoid of trendy restaurants, high end retail, etc. There was no Northern VA tech scene, no Dulles Technology corridor. It might as well have been suburban Ohio. Outside Georgetown, DC itself was a sleepy commuter city full of chain restaurants that closed at 6 pm. There was no Hermès. The Michelin guide didn’t even review restaurants in the city back then. That’s all changed completely.
So I don’t feel like comparing the price of housing back then and today is fair. You’re buying a completely different product for your money. Today, a similar place to what Northern VA was like back then would be like Crofton, MD (not to far from where I live in Annapolis). You can easily buy a house like the one I grew up in for a price similar to what my parents paid in 1989 (adjusted for inflation obviously).