I've bought from the Classifieds here, from eBay, and from reddit (r/AVexchange). Good experiences all around, just make sure the seller you find is legit. I haven't bought from Reverb yet, but am open to trying once an opportunity presents itself.
Also, I forgot the Campfire Cascade. Add that to the list of headphones that'll wipe the floor with the Crushers for your budget.
I don't mean to be overly negative on the Crushers, because they're fun in a gimmicky kind of way. The problem is that its sub-bass isn't real sub-bass, it just has vibrators in each cup that start rumbling with the presence of sounds below a certain frequency. In my experience, it was like, once there was sufficient signal below about 60hz, then the vibrators would start. But also, the vibrators don't really fluctuate in frequency or anything the way real sound does, the vibration is just one frequency, and it's either on or off. It's like strapping an N64 controller with the rumble pak to your head. I suppose it is safer in a way because the rumbling is achieved with vibrators instead of actual air pressure, so there's no (or at least much less) of a chance of damaging your hearing. But if you were to judge the headphone solely on its sound quality, its bass really isn't much better than its mids or highs, which is to say, it's really very poor. Just flabby, woolly, lacking in detail, lacking in extension. It's the vibrators that make it fun, not the actual sound. And even then, once you spend enough time with the Crushers, you realize just how "one-note" the vibrators are how abruptly and unnaturally they start and stop. Once you experience headphones that achieve the deep, eye-rattling sub-bass effect using actual sound, you realize how much more fun the effect is when it's achieved legitimately.
I'm honestly always disappointed when I see it mentioned in this thread, because it really doesn't belong here. For the same or less money, you could get a used Sony XB700 instead and get the real deal. Or you can wait for the Drop Ultrasone Sig X to drop to $200, which it does with some regularity, and get something else new for very similar money and get some actual legitimate bass. I haven't heard the Ultrasone myself yet, but based on my experience briefly owning a Crusher and seeing what people say about the Ultrasone, I already know I'd rather buy the Ultrasone, ten times out of ten.
And especially with your budget, you have so many great options that the Crushers shouldn't be anywhere near your radar.