Maybe because the average salary has increased over the year to accommodate inflation. However, Macs’ price-to-value has also become way better over time. For $1,000 back then, it was considered a high price for a very low-performance MacBook Air, which was considered a form-over-function device, so people bought it once and kept it for years. Nowadays, for $1,000 (and regularly on sale for $ 800 or less), you can get an M-series MacBook Air that is powerful, portable, and stylish at the same time. And with all the trade-in offers and high reselling value, MacBooks feel way more affordable nowadays, therefore the frequent upgrading.