Have you spoken to a "despachante de aduana"? - They are basically import agents who you need to arrange the import of the goods with. They would need to look up the tax code for the goods you want to inform (actually each component will have a tax code) , they will give you the correct amount of tax.
You would need a DNI / CUIL to import legally, i.e. to set yourself up as a new importer. You'd be straight into the "red" channel, i.e. every import that comes through would have a paper and physical inspection. The physical inpection means that your goods go straight to a "fiscal warehouse" This is a privately owned inspection point, you have to pay per day the amount of fees incurred for the stay of your goods. In practice, you have to grease someone's palm to get your shipment though otherwise it'll sit there and suck up daily fees in the warehouse. As a new importer you'll ber defenceless against that regime! I met someone a few years ago bringing clothes in from china who explained they had to go down with a large flatscreen tv to get things moving! I met with a despachante last year and they told me to factor bribes into my budget.
If you haven't already you need to talk to a despachante de aduana (not the govt body, private import agents). I was lucky to have a family connection that allowed me to have a series of chats off the clock, but the end result was that importing some small items from China was not going to be cost effective.
Sidenote, importing from a Mercosur country can be more cost effective if the price is convenient, trade off paying in reales/USD to Brasil for a less stringent customs routine and land shipping over the border.
So, you need to be legal, registered and prepared to pay a bribe on top of the taxes. If you can then make money on top of that you have done well ! My understanding is that your goods will get stopped and inspected, if you are not legal, it's possible you won't see them.