I buy my assets, and I use freebies that are licensed for commercial use. So yes it can be expensive if you rush to buy stuff without a plan. And one of the biggest fuck ups I did was not to buy PC+ (Platinum Club+) right away.
As for 3DMAX and Maya, simply time and money. While there is a indie license ($250 per year for each), but last time I checked it was available only in US, UK, Canada, New Zealand, and Australia. So the "retail" for Max license is $1,545/year or $195/month. Also blender is free alternative.
Then comes the time, which applies to blender as well. Modeling takes time, how to learn to model takes time. A lot of the developers are doing this as a hobby, or at least in their spare times. So DAZ provides working alternative to those who don't have time to model, time learn to model, or simply suck at it, mostly meaning myself with the last one.
How to start? Download DAZ3D if that is the route you want to go, with it comes basic assets that you can use to learn how to use the program. And there is a thread with legit freebies on this forum. And if you decide that DAZ is the way to go, then either buy the assets or use the resources in here if you wish.