FCC approval and quantity
No, you're not reading it right.

The exception is for less than 4000 units, not for resale and only for "testing and evaluation to determine compliance with the FCC Rules and Regulations, product development, or suitability for marketing." 

So you can import them in order to verify that they meet your requirements and the FCC rules. You can also use them for product development, testing and marketing. But you can't use them for a final product no matter how low volume.

You could in theory get around this by effectively keeping the the system they are used for in perpetual beta test but you'd need to have some grounds for claiming that. You would also have to have a very very good excuse as to why you haven't performed the required FCC testing yet.

If you are selling via somewhere like amazon then they are being sold as an end product and so the exemption does not apply.