Riffing on Jerryc41's "The Camera You Have with You" thread, a ukulele you're not afraid to play will sound much better than one that gets left in its case!
Part of my "is this too expensive" equation includes if it's pricy enough that I'd be afraid to play it. I'm pretty lazy, and if I can't keep an instrument out and at hand it's not likely to get played. My better acoustic guitar spends too much time in its case in favour of the lesser instruments that get hung on the wall year round.
There's also diminishing returns in sound quality - most of my inexpensive ukuleles sound great on their own, even if there's a noticeable difference when played side-by-side with a more expensive one (and honestly speaking, the limiting quality factor is the player not the instrument).
--Rob