A saree carries its value in how it was made, which is exactly what a photograph is worst at showing.
What moves the number
The weave and the region it belongs to.
Handloom or powerloom, which is a real difference in both work and price.
Zari — what it is and how much of it there is.
Condition, and in this category that means the fold lines, the pallu, the border and any pulled thread.
Completeness — blouse piece present, and how much seam allowance is left.
Why two of the same differ
One seller showed the reverse, the selvedge and the border close up in daylight. The other showed it folded on a bed. The first is a saree somebody can bid on. Describing saree condition.
How to find out rather than guess
Identify the weave and region as precisely as you can, and say how confident you are. Then compare completed sales of the same weave in the same condition, not of sarees in general.
Where you cannot identify a weave, describe what you can see — the hand, the weight, the reverse, the border — and let the room place it. In this category the room very often knows.
Vintage and inherited pieces
Age can add value where the work is good and the piece has survived well, and it subtracts where the fabric has weakened. Say which you think you have, and show the folds — that is where old silk gives way.
Questions people ask
Does a stain ruin it?
It lowers the price and must be shown. Many buyers will still want the piece for the work.
Is a heavy saree worth more?
Weight often tracks the amount of work and zari, but it is not a price by itself.
Should I dry-clean before selling?
Often yes for occasion pieces, and say that you did.
More: pricing sarees, packing sarees.