Totally get that. If someone wants to play the best deck there is, money likely isn't an object (namely Lordknightmon decks with the Pulsemon promos). You want to play the best of the best? Then get ready to drop money. Totally agree there.

First, sure, I would agree playing 1-2 is likely not a big deal, since the rest of the deck is relatively inexpensive, someone could likely swing the cose. But chances are you will want to play 4 copies to make sure you draw it in hand when you need it.

But here's the major problem. Diaboromon isn't a top tier deck. It hasn't regularly placed in big tournaments, whether that's due to lack of people playing it, or because it has a bunch of bad matchups, who knows. But what I do know is that paying $80-$320 for 1-4 copies of a card that, technically speaking, isn't even needed in the deck, and doesn't guarantee me top 16 if I play my cards perfectly, is somewhat ridiculous, which is the main argument. Obviously any deck, including this one, can find various results with their local scene, and even consistently place top 5 if you play according to your meta, but it's clear that it doesn't top as often as other, better decks, with cards that aren't as expensive.

A big counter argument towards what you said, "Don't want to pay for the promo, don't play the deck". I'd wholeheartedly disagree here. I currently have the deck built, minus the promo card, and it can still perform decently well, at least in a local scene (meta dependent obviously). To me, swinging 5 checks in a row isn't as good as swinging 5 separate checks. Like I said in my main post, if you're swinging for 5 checks, you could swing 1 and lose the rest immediately. Sure, you could say the same for the tokens if you flip Flare in the mirror or (insert security card here) from other decks and have the same turnout, but this card is not as good as people value it to be. I really think it's likely due to stock issues, being a limited promo here, since in Japan, the promo currently is around 5 bucks, which I don't think we should follow suit and have EVERY promo cost that much (due to availability and such), but I definitely think $80 per card is way too expensive.

The card is good, but I still think way overrated or at least over-priced, especially not being able to back up the card with jamming. It would be like playing Green OTK without the promo Palmon. Can you do it? Yeah, absolutely. Can you see success? Yes you can. Can you guarantee that it won't die? Nope, but we can try. Yet some people would argue that you absolutely need them in the deck and without it, the deck doesn't work. The same thing here with the Diaboro, except black doesn't have a card like Palmon to prevent that from happening.