The Mind card is the Seven of Swords. This card represents worries or doubts. Its presence suggests that there are some concerns about buying the watch you saw online. You need to consider whether you have enough information to determine the authenticity of the watch before buying it.
The Corps card is the Queen of Swords. This card symbolizes intuitive and insightful qualities. It may mean that you should trust your instincts and do some careful research to determine the authenticity of the watch. A good research should lead you to a safer conclusion.
The Soul card is the reversed Five of Swords. This card speaks of a refusal or failure. This may mean that you need to be prepared to accept the fact that you may not be able to verify the authenticity of the watch with certainty and that you may end up with less than what you hoped for.
Taking these interpretations into account, it seems that you need to be careful when deciding whether to buy the watch you saw online. There are some concerns about authenticity that need to be addressed before proceeding with the purchase. So, the answer to the question is No, it doesn't pay to buy the watch without doing a thorough research first to make sure it's authentic and not a fake.