I've also provided detailed methodology for comparing machine versus ink costs from two models here: http://www.luminous-landscape.com/essays/4800%20tracking.shtml
. Unfortunately it does require doing some calculations to assess the answer to this question.
OK the OP is looking for answers - let's make a few simplifying assumptions and go to it: (a) we'll assume both printers (R3000 and 3880) use the same amount of ink per sq. in. of printing; (b) let's pitch that at .011 ML (rough average based on previous observations of other Epson professional models); (c) the charge-up ink in the lines does get used for prints but a certain amount of charge-up ink also goes into the maintenance tank - we don't know how much so let's ignore it, and (d) let's use B&H pricing as the reference (the OP will have to gross-up these values for the shipping and duties he needs to pay to get the machine to wherever he lives and take account of any relative differences between ink and machine once he's done the adjustments). Once we're prepared to live with these assumptions for a rough guide, let's see what we get:(all values exclude taxes)
3880: Machine USD 1140 after rebates. It comes with USD 540 worth of ink, so the net value of the machine itself is USD 600.
R3000: Machine is USD 600 after rebate and it comes with USD 275 of ink so net machine cost is USD 325.
Difference of machine cost is USD 275.
Ink for the 3880 costs 75 cents per ml.
Ink for the R3000 costs 1.23 dollars per ml.
Difference of ink cost is 48 cents per ml.
The amount of ink you need to consume before matching the machine cost saving on the R3000 with the saving on ink in the 3800 is USD 275/0.48 = 572 ml.
This amounts to 52,000 square inches of printing (572/.011).
If we use an 11*17 inch printed surface on a 13*19 inch sheet, that's 187 sq.in. of ink coverage per print.
52,000 sq. in. / 187 sq. in per print = 278 prints.
So if you print 10 per month, within roughly 28 months of printing you'd get your money back buying the 3880 rather than the R3000.
This is just an illustration of the logic process using believable values that are valid in New York City. It is not a hard and fast evaluation totally relevant to your situation. You need to make adjustments of values for your situation. But using this logic process you can answer the question for yourself using numbers that relate to your delivered costs. Looking at the matter strictly from a cost perspective it boils down to how many prints are needed before the saving in ink outweighs the saving on the machines and how much time you want to wait for break-even.