Isn't that illegal, unless it is for personal use?
I don't think it's a problem.
I know from experience, when I've ordered products from the U.S., and they specified a wholesale value on the declaration (the value specified was significantly less than what I paid ... it was obviously the wholesale value).
And these were purchases from a well known, well established, medium sized business. So it's evidently their standard business practice to specify the wholesale value on the declaration. It's to their customer's benefit for them to do this (providing it's permissible by law, as appears is the case).
Regarding the value of goods shipped, the only time the U.S. government would care, would be for BIG DOLLAR shipments, costing in the thousands (ie, sending jewellery through the mail), which would be scrutinised to see whether it's a form of money laundering.
But for small value shipments, why would they care ? It's not as though they levy an "export tax" on the value of goods sent.
Obviously the foreign country where the goods are being received would prefer to have the retail price specified, to levy their import duties. But the taxes charged by foreign governments would be of NO CONCERN to the U.S. government. And U.S. companies only to need to abide by U.S. law - they are not bound by the laws of foreign jurisdictions.