A Big Mac meal in the states (fried and drink) cost 2.99 USD in 1990.

It now costs around 8.50 USD.

The inflation adjusted value of 2.99 USD in 1990 is about 7.88 USD.

Did the price go up? Sure. Are you likely getting slightly more in 2026 than you were in 1990? No idea, but it seems plausible to me.

Inflation is the answer.