LEDs don't have enough power to actually light anything, by several orders of magnitude.
Yeah, my biggest concern with the $40 one is that in the specs it lists a power of 15GN, which isn't very much at all. It says, "also great for portrait photography" too, LOL. This doodad isn't going to light anything that is more than 2 feet away from the lens.
I dunno, Jen. I think you'll be disappointed with that one, but considering the high-priced alternatives, it might be better than nothing. It's only $40, so you're not betting the farm if it doesn't work for you. I just wouldn't get your hopes up about it taking your macro photography to the next level.
You might want to also take a look at this one
, which is $100. It's an actual TTL ring flash with 46GN power, 3x more light than the one above.