I am not sure if i can follow. Here is my math:
We have 19.83% of the total shares transferred.
If the source is correct and 51% of those shares are sold to Apollo Investors that’s 10.1% of total outstanding shares or 40.48million shares.
Vonovia said they get a bit more than 1 billion in liquidity.
Considering fees for the transactions a sell price of around 1050million might be reasonable. This translates to a price of EUR 26 per share. (1050m/40.48m)
Vonovia might argue that this is the price third party investors are willing to pay and the price which is fair to offer in a share swap.
I think the purchasing agreement is likely conditional to make sure it works well in the context with the entire restructuring (DPLTA & offer to swap shares)