As a long time guitar collector - both vintage and new - and now the owner of 2 ukes with a third having been sold, I can understand the "try it before buying it" sentiment. It makes perfect sense and for those who have access to a variety of the instruments they want to play, and I would avail myself of that opportunity without hesitation. However, for those of us who live in areas where the instruments we have an interest in are not to be found, that is not such a practical option. Let's say I want to try out a Mya-Moe walnut tenor cutaway or a Moore Bettah concert koa with cedar top, well, my chances of finding one of these to test drive in my neck of the woods is between slim and none, and none just left town, if you get my drift. Sure, ideally I'd like to simply cruise down to my neighborhood Mya-Moe or Moore Bettah outlet and try out 20 different varieties of each and then walk out with the one that flipped my switch, but that just isn't going to happen.
Second, the sound of new instruments varies from instrument to instrument, depending upon a lot of factors, not the least of which is that some identically made instruments just end up sounding better than others for no other reason than they just do . - go into a big music store and play 5 Martin tenor ukes - I guarantee some will sound better than the others and one will stand out above the rest. Meaning that if I am somehow fortunate enough to play Ukulele Bob's Mya-Moe mahogany concert and it sounds wonderful, there is absolutely no guarantee that the identical instrument I order from Mya-Moe will sound the same.
So, what's a poor schmo to do? Well, we read reviews, talk to folks who have owned the instruments we're interested in, watch YouTube videos featuring those instruments, and then pull the trigger on what we "perceive" is the one that will serve our interests and hope that it meets our expectations. When they don't, you find them listed in the Marketplace. Not an ideal system for buying a custom uke I grant you, but the only real option many of us have. In the final analysis, if you buy quality at a fair market price, you will at least improve your chances dramatically of recouping most of your investment if the instrument doesn't live up to expectations.