Sounds like a deal...

"We have enough silver. We are in need of guns. Lots and lots of guns. And the black fizzy drink that seems addictive."

The Inca on easier modes will always go to selling silver for 50 and will pay close to 2000 for each stack of tools/trade goods. European prices aren't part of the calculations at all. The capital will pay more and will sell full stacks of silver for 50 but even normal cities will pay high prices and sell 25 silver for 50...

The plan is, play dutch, sail south to the Inca, land your starter troops and send ship back to Europe for tools/trade goods, trade this to Inca city.. negotiate about 10 times before accepting on sale and just accept price they offer for silver.. . get galleon asap and keep running through tools/trade goods until the prices aren't worth it and the Inca are annoyed... then conquer them.

Yes, yes they do.

Do European prices have any effect on trade negotiations with the natives?

I've been offered some stupid shit on my current playthrough, but this is ridiculous

A fairer price would be 25.

seems legit

Round deal... ;D

fair trade