Project New Weapons(Hephaestus)

[Enzyme]

why not replace the old weapons with new weapons in terms of what the new weapons are worth?

Because this would also create drama. 

Players who had paid for a certain kind of gun would have their weapon changed into a weapon that they never paid for. An example can be the old Galil and the new M14 EBR. Both have the same price, but they are very different.