I think people have lived taking several mg or even 10 of 25I but what I don't think is that they considered it even remotely suitable for repetition. So IMO that is what is what makes your reported doses so curious, suspicious I will say.
Not that I am actually making it about credibility whether you have 25B or DOM or mescaline, or not... but if nothing else, it could be extremely dangerous if say your 25B is cut (is 300 ug of it quite active?), and you think that these dosages are normal, and would then come across veritable and pure psychedelics as potent as the ones you mention. Recipe for OD.
Price discussion is not allowed. But dose for dose, yes it's one of the most expensive psychedelics usually. I know when I got it I, too, was very fortunate both of the times. One time for free (unexpected favor for favor), the other time opportunity for very affordable stuff.
My trips were all consistent with mesc for sure, but only one of the batches is fully lab-verified.