Let me tell you about this as I have much experience in this matter.
When there is an invoice of more than QR 500, you always stand a chance of having to pay customs.
Certainly if it is expressed. Lower chance if through the mail. Dont ask me why but it is just lower chance if it comes through the post office.
Your best is to have forwarded to family in the states then have them resend it USPS global priority WITHOUT an invoice.
You can ask Amazon not to include an invoice but i dont think they will.
Customs here in Qatar is certainly one of the most unfair entities you ever wish to come into contact with.
For starters, if your final invoice cost is inclusive of the shipping charge, customs will include it as part of your QR500 limit. Can you believe it? Ridiculous. And there is no way around it. So the QR 500 limit is not just the cost of the merchandise as it should be.
When I learned that I lost total respect for the customs authority as a cash hoarding beureacratic unethical entity. So it is imperative you make sure at least the shipping charge is off that invoice paper.
If the charge is just %5 as it should be there would be no problem, but the add-ons charged make it impractical to bring items in.