Now you can see from the Market screen that 3 jumps away someone is buying trit for 3.00 each. That's over 10% more, but you have to move those minerals to the buyer. Like items, minerals take up space, just a lot less of it. But they do add up. Unless you have bought a hauler, you probably only have 300-400cm of cargo space free. Let's use 300cm for our example, so you can haul 30,000 trit at a time.
We melted a whole bunch of mission junk and have 25000 tritanium.
Sell Local: 25,000 @ 2.70 = 67,500isk (0 jumps - no time spent)
Sell Away: 25,000 @ 3.00 = 75,000isk (3 jumps - 10 minutes spent)
You have spent 10 minutes to make 7,500 isk. Not a good return on your time.
But what if the spread is more pronounced?
Sell Local: 25,000 @ 2.00 = 50,000isk (0 jumps - no time spent)
Sell Away: 25,000 @ 3.25 = 81,250isk (3 jumps - 10 minutes spent)
You have now spent 10 minutes to make 31,250 isk. Better, but not great.
But can't I make it up in volume by saving up my trit and selling 90,000?
Sell Local: 90,000 @ 2.00 = 180,000isk (0 jumps - no time spent)
Sell Away: 90,000 @ 3.25 = 292,500isk (3 jumps x 3 trips- 30 minutes spent)
You have now spent 30 minutes to make 112,500 isk. You had to make three trips since you could only move 30,000 trit at a time, due to your cargo hold. Now you might have other minerals or items you want to move, so those trips might be worth it. The thing to realize is that even a large difference in price could end up not being worth your time.
Traders can move huge loads easily, but even they have issues with larger volumes:
...have rigged my Mammoth with cargo rigs so it now holds 27,129.3 cubic meters. That's 2.7 million trit per full load. And the end is still nowhere in sight.
A full load of trit takes about half an hour to haul and is making me a million isk. That's not really worth the time.
That's a quote from Stabbed Up, describing how even with the ability to have an insanely large hauler, it just doesn't pay to move large amount of minerals around.
You aren't a trader, you're just trying to make a little more isk. Use the spreadsheet from my last post and put the expected market value in there. If 2.1 for trit is what you can sell each time at your station, then use that number. If the buy orders at your station are actually higher than that mineral value, sell the item. Let the other guy deal with the melting and hauling.
A hauling tip for those of you who just need to sell your minerals in another station:
Look at the number of minerals you will get for an item - if the item takes up 5cm of cargo space and the total number of minerals is over 500, it is better to move the item and melt it down when you get there. For a 10cm item, use 1000. You might end up being able to move a lot more and maybe even sell those 90,000 trit in 2 round trips instead of 3.
Sure, it is a little math, but c'mon, we're playing EVE, we all love math! If you can figure out transversal velocity and falloff ranges, you can learn how not to get fleeced when selling stuff.
Disclaimer: I know I am leaving out things like fees and standings again, but this is theorycraft and I can do what I want.