Out of Home is still a great value versus other forms of media.
Here’s a chart from the PJ Solomon March 2021 Media monthly which compares the CPM (cost per thousand views) of out of home versus media and online advertising. Bulletins and posters have a CPM cheaper than TV, Podcasts, radio, mobile video, desktop video, newspapers and magazines. Only mobile display and general display ads are cheaper.
Source: PJ Solomon March 2021 media monthly