I think for normal sellers like us (with relatively small collections) it's very hard to make conclusions based on our sales.
For me the most indicative data is the one that 3d_Molier shared on TS forum - he wrote that he experimented and was always at loss when participated in discounts.
He has the largest and most diverse collection on this market, so I think his conclusions are the most accurate.
Even if you make higher number of sales in the end you make less profit, especially with large discount % (have in mind ,at the time 3d_Molier shared this ,TS max discount was 30%)
I think the true is, discounts are used mainly as a weapon to kill competition.
They can work for certain types of mass products that appeal to large groups of people like computer games (or potatoes), but on our specific market individual sellers will lose in 90% of the cases.