I have a high-quality pair of suede boots in my closet that cost ten times what I usually spend on shoes. I bought them when I was living in Boston, to replace a cheap pair I'd bought in southern California that weren't keeping my feet warm. The expensive boots are comfortable and have held up well over many years. But unfortunately, now that I've moved back to SoCal, they don't get much use. And if I were to move to, say, Portland, I don't imagine I'd wear them much because rain and suede don't mix. They were perfect for New England's dry, chilly autumn days, and for cold winter city sidewalks that had already been shoveled, but they're too much and also not enough for the weather on the west coast.
That's a bit how I feel about GUE training at times. If you just want to go a little deeper than you can snorkel on a tropical reef, you might get everything you need from the training equivalent of a pair of flip-flops. And if you want to brave surf entries, or learn self-sufficiency so you can focus on hunting/photography/doing your own thing without worrying about a buddy, or if you want to dive a particular wreck in the 100-130 foot range without selling a kidney to fill your tank, you may find that the training equivalent of a pair of rubber boots does the job you need cheaper *and* better. I guess it's a good thing my suede boots can't talk, because in some ways they really are better-quality shoes than the ones I'm wearing. And yet...