What you describe is smoke testing. However, taking money and not having a product is considered fraud in the US. The way you get around this is that on the final confirmation page where you would normally take payment details you instead say the product is on backorder but that the person can enter their email to be notified when it's available. That'll give you the stats you need without running afoul of the law or dealing with payment gateways for payments you are not really accepting.