Speaking from my own experiences, I think the dumbest money is spent buying golf equipment that you're not fit for. People spend so much on putters and drivers because they're looking for the magic stick that will sink every putt and send every drive down the fairway 300+ yards. Golfers spend thousands of dollars chasing the latest marketing craze and never find the magic.
I played a round last week with a business associate that played Hogan Apex II irons, Hogan woods, and a Bullseye putter. He shot an 82 after having not played a round all summer. He could hit the ball 280 yards on his drive and he appeared to sink every putt within 10'. He paid $50 for the entire set, including the bag, so much for needing to spend thousands. He said he owns newer drivers, new irons and even a few SC putters but he doesn't score as well with them, he said I guess these clubs just "fit" me.
I agreed in that I've spent a lot of money on putters only to find out that what appealed to my eye didn't fit my putting style. Turns out that while I like the look of a blade putter, the #9 is better for my putting style. I could have spent tens of thousands on blade putters but if my putting style didn't change I wasn't going to have much success with them.