I know somebody who bought out the VPO about 5 years ago on Riviera (Caronte)
They paid about 1000 euros.
The money was paid to the Junta de Andalucia,who originally lent the money to the builder.
It will probably be less now and can be deducted from the sales proceeds once
a certificate is obtained from the Junta showing the amount due
Your administrator should have details of the procedure.