I strongly agree with this proposal.
From my experience, a promoted team has a big business opportunity that must be exploited in an attempt to improve the team (in order to avoid relegation). A team that just relegated will have about one half of the previous supporters (plus a drop in merchandising even two weeks after the relegation), so dropping prices could at least be useful to keep more people involved and to try not to have a half-empty arena... that is soo sad.