Another factor is that the difficulty of having to 99. Playing effectively it requires N hours to degree strength to 99 that means you can safely assume that the whole RuneScape players above 99 have spent at least N hours training combat. If N is high that means a large section of the RuneScape players have played RuneScape a whole lot, and you'll be able to compare this number to the number of RuneScape players using low stats to make a judgment about the number of RuneScape players that the low-level (say under 50) articles is really catering to. But again it's not perfect because people do not train stats at the exact same rate and some RuneScape players don't train battle in any way. RS3 solves this problem by making becoming to 99 easier so that if you are brand new you do not have to play RuneScape for 20 years to be in an even playing field with those who have been enjoying RuneScape for 20 years.
I know that exists. However, why would jagex not implement another money sink in to RuneScape that is a QOL at every facet? There are already plenty other machines such as the board manufacturer, auto disassembler and auto alcher that takes it's place and the NPC is futile as is. Wouldn't hurt the market at all? If people want to make profit off unf potions, go use this equipment, if people want unf potions quickly and are eager to devote the gp, then go to the NPC. We already have a little niche in creation for this, which is as much of a money sink with celestial charges.
It is a divine charge sink, not a cash sink. There's no money being eliminated from RuneScape. Divine charges cost cash. Or they take the time to create which you might have spent earning money. It will not take money right away, but it will have a charge to cheap RuneScape gold maintain running. Divine charges are arguably a time sink 1 way or another, since someone must spend some time making them and they operate out after a period of time. But you're right they're not a cash sink, since while they do cost money, by purchase or opportunity cost, they don't get rid of any money from circulation.