if a pickup isn't installed

is that portable one that Aldrine has showed us before, anywhere near the comparison?

not really and it leaves a sticky residue on your uke (at least it did for mine)

Apples and oranges with that sticky one. I think you should just invest in a proper UST, and play the uke for a long time. I've got a Taylor Guitar from 1992 with a Fishman Matrix in it. And it's still working perfectly. So these pickups last a long time. Depreciate the $200ish cost of the pickup+installation over about 18 years, and that's just a hair over $10 a year. Not bad.