It's impossible to put an exact price on the soul, as it's an intangible concept with a lot of different interpretations. However, if we look at the soul as an integral part of the human experience, it could be argued that it's worth more than anything else in the world.
The soul is what makes us who we are, and it's the source of our consciousness and identity. It's what allows us to love, to feel pain, to experience joy and sorrow. It's what makes life worth living.
There's no way to put a monetary value on something like that. But if we consider the soul to be the most precious thing we have, then it's safe to say that it's priceless.