That's wishful thinking, especially for DR Harris. A hard milled soap like DRH or Tabac probably has as much actual soap in it than the 250gramme MdeC.
For what it's worth, as someone who has and likes both, especially Almond scent, I go through D.R. Harris a lot faster than I do though MDC, and price per gram is not "that" far off. 200 grams of D.R. Harris is $56 Canadian where MDC is apx. $66. In my experience D.R. Harris needs a lot longer to load than MDC does.
Tabac (which I also like) I don't consume as fast as D.R. Harris and is indeed a bit less (about $40 CAD for 200 gr).
I haven't done exact measurements, so no, I would not bet big money on this.