Woodcutting Being My Greatest Of Them

Hi, I'm one of the people who HAVE to understand what is going on around them (not people's business, no, I'm not nosy ) but how things work. And, I've been fletching willow longbows (u) and selling it to overall shop seeing that OSRS gold  nobody will buy them in 83 gp ea anyway. How can the general shop work?

But, also, I've noticed that in certain fansites, they've listed items to get the same low alch money gained as they market to the general store but it is not the case for willow long (un ) since if you low alch them, you buy 64 gp ea but when selling it to general store, you buy 16 and also the STORE sells for 64gp ea. I was wondering if there was a common equation is effective for all things for general store or are there exceptions to certain items?

I had been wondering about that and that I looked around the thing databases of several websites. . .This one website said that it costed 0 gp to purchase an Armadyl godsword in the general store which is certainly not possible so I guess they supposed N/A or did they mean that you can't purchase it from the Rs2107 gold  general store? Please inform me that the rule or something which is communal for many items so that I can put my fascination in the rest or that I probably might start selling all my stuff to the general store and purchasing them again...