Impossible to gauge DDR4 vs DDR5 price declines when the quality of the chips is not known. A DDR4-3600+ C14 kit is just as expensive as a DDR5-5600 / 6000 kit with Samsung chips right now (~$230) and cheaper than the Micron stuff (Usually DDR5-5200 and below), but a DDR5-6000+ with the good chips (SK Hynix) @ C36 or lower is significantly more expensive ($300++).
i.e. the best of DDR4 (B-Die) is still quite a bit cheaper than the best of DDR5.