Over the years I have often suggested larger animals to some people usually it’s based on their expectation or including a kid factor in the mix where I will always recommend an animal 500 grams or up (since they are more foolproof handle better compare to hatchlings.
Now the issue is really supply and demand and therefore price, and usually adult females are at a premium (so yes you save money on the food you did not have to offer but you don’t save that much money).
So buying bigger animals is not easy from the pet owner perspective that does not want to pay the premium of a snake that can breed and make a return, and as a breeder you sell an adult pricing will be the same whether you want it as a pet or breeder.
Now they could always adopt an older snake but that too can come with a set of issue and can quickly become a costly nightmare.
My main issue with some buyers and some breeders in a hurry to sell not have to house or feed is that we see (here for example) a lot of people that have animals that they should never have bought or should never have been sold to them, when you sell or buy anything under 100 grams it can go sideways very quickly and I have seen it on this forum too often, sadly as long as some people will sell babies out of the egg or with one meal in them and some people will buy them and then do what they want to do rather than what NEEDS to be done, it’s never gonna stop.
I think people need to release that their expectations are often too high and that yes older animals would be a much better fit for them.