The big difference here is that by the time the 2080 had saturated the market, you could regularly find a 1080 for ~$300 (I paid $275 for an EVGA B-stock model).
Whereas today, with the 5000 series in the market for quite a while already, a 4080 is still well over MSRP
Whereas today, with the 5000 series in the market for quite a while already, a 4080 is still well over MSRP