From my experience with TCGs, prices vary very heavily. Hell you could go out and buy a single card for $16k(or not be an idiot and spend that money elsewhere)
More likely than not, there probably is too little demand, but too much supply. I've seen it happen over and over: Products get hyped up, but if it bombs, nobody wants it so in order to make a profit sellers rack up the price a ****-ton. Doesn't help that Bushiroad secondary markets tend to be pretty wack because of how obscure they are overall.
I also wouldn't call it merch, but whatever floats your boat.
On another note, Ebay is like the worst place to check for prices, TCGplayer is the end-all-be-all of market prices.
For example:
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For an extra booster(aka a booster box that contains less cards and is meant to be cheaper) that's a damn bargain If I've ever seen one!
Or how about this:
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$60 bucks?! for a booster box from a game that naturally has "anime tax"(aka people up the prices simply because it's anime) that's cheap AF!
And lastly
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hmm, not much to say about that. It's your standard Bushiroad TD prices.
My point is that Ebay is not a good indicator of the value/market price of an item, especially because Ebay gives incentive to over-value all your crap, which ****s with the idea that stuff will "naturally" go to whatever value the market assigns to it(they take a VERY big portain of any sales you make, trust me I've tried selling stuff before. Anything you sell under like $3 is only gonna make a $1 or $2)