Yes- River Place is on leased land, and there has been an impasse between the cooperative and the landowner dating back to this 1982 Post article...
https://www.washingtonpost.com/archive/realestate/1982/01/23/river-place-co-op-is-selling-borrowed-time/f4d72370-f529-4994-8562-86862b1e73f3/?utm_term=.26a2eaa777fa
...that to this day has yet to be resolved.
I wondered the same thing (isn't this really cheap?) when I was looking to buy a place last year. You can get a spacious 1 bedroom apartment, in a great location, with a balcony and river views for less than most basement studios... but it's a gamble. Would love to hear what any current residents have to say about the land-lease situation, and if there's a resolution in the works?