While I only have knowledge of a few of our favorite boobie greed girls OF prices, Foxy normally charges $1 less than Beshine and half of that of Mary. All update an average of daily, but Mary probably hits twice as much and posts those short like 10 second videos as well.
When it comes to video purchases, Beshine is cheaper ($19), Foxy seems to base price on length, but it about 150% higher than Beshine, and Mary is just kind of insanely high. One huge difference is Beshine offers a new video every other day, while Foxy is more like Mary, maybe a couple a month. The videos are rather repetitious with the exception of Beshine videos dealing with a variety of daily activities where her boob size is creating "enormous boobie adventures." They are much more entertaining than the base modeling.
Of course, if you are looking for interaction, Foxy is tops; frequently reading and responding to remarks people make and using the PM for conversations she wants to pursue. I have had Mary respond on a few instances to a comment I left, but have rarely seen her respond to others; guess you have to spark her imagination. Beshine, I doubt she looks.
Different girls, different approaches to life, expectations, and interactions.
As far as lower prices attracting more members, I think it may nudge the needle a bit, but like I have pointed out before, when implants pass a certain subjective volume, fans/members/followers seem to actually decrease. I cannot say how many OF members they have but if you look at social media, you can see the correlation with a 4k girl having 10x the following of a 10k girl. There are just fewer of us around that find enormous breasts hugely attractive.