First, items marked as "Salvage Item" shouldn't be salvaged by you. You should sell them on the Trading Post (TP). The same applies for opening any bags you collect. Why? Well, you have to trust the market and assume that, on average, the price of bags reflects the value of what you get out. You might get lucky but you probably won't. So, why risk the RNG yourself? Take the average profit as opposed to the chance of a big win or a big loss. Most importantly: don't salvage or open bags for mats to craft with. More on that below.
Second, level 68+ Rare and Exotic equipment yields Globs of Ectoplasm at a rate of about 0.875. However, since this is again RNG, I'd look at this link and if the item you are considering salvaging sells for more than the current Ecto sell price you should just sell the item and let someone take the risk. If you salvage you have a 15% chance of getting diddly squat. Why bother?
Third, Essence of Luck was introduced to reduce the gold coming into the economy from NPC sales of blues and greens, which were (at the time) basically worthless. However, once you reach about +70% Magic Find (MF) the amount of luck you need to reach the next 1% starts to get quite steep. Unless you farm high-value loot constantly boosting your MF isn't really a great investment so consider selling you greens to NPCs for the cash (3 greens are worth about 4 silver) instead. Blues are worth so little you might as well Crude Salvage kit them. This is especially true for level 80 greens and blues were T5 mats are in massive over-supply and hence worthless. The exception here is light armour. Cloth mats have increased significantly in value with introduction of Ascended armour so look to the TP for profits on those first!
This screen capture of my recent TP post history gives you an idea of the figures that might be involved:
|Unopened bags, light armour and a rare - cash without the RNG|
1) You're level 40 and need Vials of Weak Blood to craft. You would be better of farming Vials of Thin Blood, selling them and using the profit to buy the Vials of Weak Blood. Always farm items with the highest value.
2) Let's say you farm 1 gold worth of T6 mats and, with 50s of other components bought from the TP, make a 3g value item. How much profit have you made? 1g 50s. Yes, you didn't pay gold for the T6 mats but you could have sold them for gold. Crafting does add value to mats but don't fall into the trap of thinking it's not costing anything to craft with mats you farm: it's "costing" what you could have sold them for. On the bright side, if you're levelling a craft, that "cost" is the price you pay for skill ups.
So, there you have it: my tips for making a slow buck in GW2. Don't leave it to chance.