What is the hardest card to get in Yu-Gi-Oh cards?

Answer 1

Rainbow Dragon - Not anymore, although it was one of the harder cards to get, along with Il Blud, 3-4 years ago, when Tactical Evolution first came out.

Right now, it is Tour Guide from the Underworld, a secret rare from a recently released card set, Extreme Victory (EXVC). It was $30-40 when it first came out in May, but more because of the artwork than the effect. Since then, it has gradually risen in price. By the end of July, Tour Guides were going for $70 each on ebay, since players knew that it could be used in many more decks once the next set, Generation Force (GENF) came out. Then, at YCS Indianapolis, which was held on August 4-7, they changed the TCG rulings for XYZ monsters stating that monsters used for an exceed summon are on the field, for example, allowing Sangan to be searched, so the price jumped right to $100, and by the end of the weeekend, it was $125. Since then, it had risen in price by $25 per week until the end of the month when it sold for a whopping $200!! Then they changed the ruling back, so monsters like Sangan, Goblin Zombie, and Reborn Tengu would not get their effects, so the price dropped to $80-100. After YCS Toronto, the price again increased to $120-140, which is because even without XYZ material effects, Tour Guide is still an instant 1-card exceed summon, and it is a secret rare, and it has yet to be reprinted, making it both hard to find and expensive.