How much can you safely pay for this lens?

How the safe purchase ceiling is worked out

Net proceeds = sale price - selling fee - shipping - reservesMax purchase price = min(net proceeds - target profit, net proceeds / (1 + target ROI))

First work out what a sale actually puts back in your hand, then solve backwards for the purchase price that still meets your target. Two targets are used because an amount and a percentage do not police each other. A 50 dollar profit target is 5 percent on a 1,000 dollar lens and 50 percent on a 100 dollar one. An ROI target alone lets the absolute margin on a cheap item vanish into one shipping label. The stricter of the two wins.

Why several exits instead of one

Selling the same lens to a dealer is cheap and immediate, while selling privately pays more but takes longer and may not happen at all. This calculator lines up the dealer quote and the conservative, base and optimistic private prices on the same terms, then treats the ceiling that survives the most conservative exit as your safe line. A verdict of negotiate means the band where the base exit clears your target but the downside exit does not.

What this does not answer

It does not pull market prices. The prices are what you looked up and entered. A dealer quote can drop after physical inspection, so it is not a guaranteed floor. Whether the lens sells at all, and how long it takes, is also not calculated. Holding days exist to produce the monthly ROI figure, and if that input is wrong the monthly figure is wrong with it.

Questions that come up

What is monthly ROI actually telling me?

The same return is a different deal at three days than at sixty. Monthly ROI stretches the figure to a 30 day basis so two holding periods can be compared on one line. It does not claim the return repeats every month.

Why subtract reserves up front?

Cleaning, repair, and return or dispute risk are costs with a real chance of landing. When they do land the profit shrinks, and nobody redoes the arithmetic at that point. Taking them out at purchase time means the number left over is already defended.

Is entering zero right when I have no dealer quote?

Yes. A zero drops the dealer exit out of the comparison and makes the conservative private price your downside. That models having nowhere to offload immediately, so the result comes out more conservative.

Can I trust the fee presets as they are?

Each preset carries the date it was recorded. Platform policy changes, so confirm the current rate before you trade and switch to manual entry if it differs.

Do the condition checks feed into the calculation?

They do not, because condition is a question of whether you looked rather than a number. Unchecked items mean the repair risk is that much larger, so the right use is to raise your reserve or hold off buying.

The verdict says pass but I want the lens anyway.

Lowering the target changes the verdict. That is not the arithmetic changing, though — it is the bar moving, so it is worth recording why you moved it. The verdict is only your result measured against your target, and the target is set by a person.