Yep. I agree. You can't really compare Apples to Oranges. That said, you should be asking, what cheap Ukes compare in sound with each other, or quality Ukes sound compared to each other. Buy what you can afford to. If you go cheap, get the best sound for what your budget will allow. But even that said, it depends on the sound you are happy with, and that can even change depending on strings, and other factors. It is very hard to target. Besides that, its hard to tell you a sound, other than "mellow", "Bright" etc. You would have to hear it for yourself. It's like "seeing" a sound I guess. I have a Lanikai LU-21 for a throwdown Uke, and it sounds pretty good for a cheap Uke. But I have different strings on it, than I do my good one, which sound "brighter" too. I then have what I consider a good Uke being an Ohana SK-35. The Ohana might be considered a cheap Uke to some, but I like it, being a solid mohogany, has an awesome mellow sound, but I also have Aquillas on it. Then I got a Harmony Banjo Uke. Not sure if it is considered a cheap one or not. I think it was a beginer Uke in the 1930s, and was probably pretty cheap and cost 5 bucks or so then, even though I have as much in it as I do my Ohana today. It sounds COMPLETELY different than the other two. It has a tinny banjo like sound (go figure, lol)...
Really, I guess what I am saying is that is a very difficult question, especially comparing the taste of an Apple to the taste of Asparagus..