The seller's job is to sell the vehicle. Your job is to understand the vehicle, the numbers and the risk before you commit.
Build a realistic market range
Search for several vehicles that closely match the year, trim, mileage, drivetrain, title status, major options, and region. Remove obvious outliers and note whether advertised prices include special conditions. That creates a market range instead of a single magic number.
Adjust for the actual car
Now account for service history, tires, brakes, accident history, cosmetic condition, remaining warranty, keys, modifications, upcoming maintenance, and inspection results. Two identical model listings can deserve very different prices because the next 12 months of ownership may look completely different.
Add the transaction costs
For dealer purchases, look at fees, taxes, registration, financing, and optional products. For auction purchases, include buyer fees, transportation, inspection, and a repair allowance. For private sales, account for registration and any immediate compliance or maintenance costs.
Create three numbers
Use a target price, an acceptable price, and a walk-away maximum. This keeps the negotiation focused and gives you a plan if the seller will not meet your preferred number.
Bottom line
Do not let urgency replace verification. Compare the market, understand the history, inspect when appropriate, review the complete transaction and decide your maximum before emotion takes over.