small Epson to proof 7880 inkset?
The smallest printer using the same ink (Vivid K3) is Epson 3880, not exactly a small printer. Moreover the ink layout algorithm (dithering, dot placement, LUT) are significanlty different so I dont think that you should expect print matches.
The best thing you can do is ask for printer profile from Costco (it may be on their website already) and then soft-proof on your (calibrated) monitor.
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