EF shows a bunch of cheaper fare filings that are valid from 1/4 to 3/9 (although some started on 12/21/21). After that, there are only considerably higher fare filings that are valid. In the case below for DTW-DEN, the cheapest valid fare filing after 3/9 is a ILNVW2H fare with $144.58 base (EF includes 7.5% US excise tax -- true base fare is actually $134.49). Don't know if I'd call it a "wall", as opposed to just a lack of cheaper fare filings with validity dates beyond 3/9. I'd check again on Tuesday when they usually load fare sales. The ILNVW2H fare below is actually still a WGA fare, so not all WGA fares currently expire on 3/9.