I don't have exact numbers, but I'm pretty sure you can get significant discounts starting around 100 parts. So not much at all.
Another thing to note is you can already get parts for significant discounts in 1-off quantities through legit Chinese distributors like LCSC. For example, a XC7A35T-2FGG484I is 90$ on Digikey and 20$ at LCSC. I think a personalized deal for that part would be cheaper than 20$ though...
I don't have exact numbers, but I'm pretty sure you can get significant discounts starting around 100 parts. So not much at all.
Another thing to note is you can already get parts for significant discounts in 1-off quantities through legit Chinese distributors like LCSC. For example, a XC7A35T-2FGG484I is 90$ on Digikey and 20$ at LCSC. I think a personalized deal for that part would be cheaper than 20$ though...