Are items imported into brazil taxed at the rate of the invoice or some arbitrary rate they determine based on content/value?

Are goods entering Brazil taxed at the receipt value (i.e. the amount paid for them on an invoice/receipt of the exporter) or are they taxed at (whatever) rate the Brazillian authority believes it to be?

For example: Every now and then local jewelry chains have sales where I can obtain a silver ring with lab created sapphire that normally retails for $80 and buy it during a special sale for $20.

If I bought 5 of these and shipped them to a relative in Brazil via regular postal and let it be taxed at the under $500 60% rate would they tax it on the $100 I spent ($20/ring) if I included the recepit showing what I paid for it. Or, would they tax it some other rate (maybe the $80 regular retail)?

This seemed like a nice way to help a friend there make some money. As the amount is below $500 (at the $20 or $80 rate) I assumed it could go regular postal with no export/import license required with it being taxed at a flat 60% rate.

Would this fall under code: 7113.11.0000 or 716.20.100 (or another code entirely)?

Kevin
Marx