Value the other item independently

The person proposing the trade may state their own trade value. Treat it as a proposal, not an objective fact.

Build your own valuation by considering:

• comparables;
• condition;
• accessories;
• originality;
• availability;
• ease of resale;
• any required costs or work.

Only then compare your estimate with theirs.

The difference between the two valuations is part of the negotiation, not an error that must automatically be corrected.