I found that surprising, so I looked on Wikipedia.

Soyuz-2 capacity to LEO: 8,600KG

Falcon 9 capacity to LEO: 22,800KG when expended, 17,500KG when not.

Soyuz-2 Cost to Launch: $35 Million

New Falcon 9 Cost to Launch: $70 Million

Used Falcon 9 Cost to Launch: $50 Million (cost to SpaceX: ~$25 Million)

Soyuz-2 cost per KG: $4000 (data from 2018)

New Falcon 9 cost per KG: $964 when expended, $1250 when not.

Use Falcon 9 coster per KG to Customer: $893 when expended, $690 when not

So realistically, Falcon 9 is roughly 20-30% the price per KG when new, and dropping to a minimum of 17.25% of the price when used.

Plus you get a larger diameter payload fairing and the ability to launch a payload up to 4X the size.

I'm pretty sure that even used as an expendable rocket, 1/4 the price per KG (if you need the capacity) is a pretty significant improvement. Now I understand why satellite ride-shares are so popular!

Plus, the Falcon launch cadence is infinitely better than Soyuz 2. 2025:

Soyuz-2: 12 launches

Falcon 9: 165!