Big Hit was already paying to distribution for BTS's albums before that. They're will still pay after this deal, but probably less. For example if before that they pay 15%, after that they will pay 10% or maybe less. Thus, more money will be left in their pocket from album sales, they will earn more. YG + will of course grow and profit thanks to this share paid. It's a win / win station.
If YG artists join Weverse, it will be a great convenience not only for the artists but also for the fans. Because when there are concerts, you will have the chance to get your ticket with pre-sell without the stress of Ticketmaster thanks to Weverse, which is one of the biggest advantages of Weverse.