I don't understand the point you are trying to make, but there are some flaws. When I do salvage I kill everything that can drop alex. Each run takes about an hour, sometimes I go under some times I go over. Not counting runs when 2 linen pouches drop I average about 120 alex a run. So really that 136 million gil would be more like 216 million.

Another problem I have with the comparison is the money you can make from the events shouldn't be the measuring stick of whether or the drop rates need to be improved. The prices of HMP and riftcinder are so high because the demand out weights the supply, because the supply is low. The comparison that should be worked out is hours to hours. I'm just going to go with your worked out number of 650 hours to farm for an Empy weapon. When you compare that to the 250 hours it would take to get 30k alex it's seems unreasonable to make an empyrean weapon over a mythic event though mythics tend to be superior.