I posted this earlier but it seems worth repeating...
So according to Marca, the financials for Lo Celso are as follows:
The loan is until 30 June 2020 and we pay €16 million. The puchase option, compulsory if we qualify for the European cup, optional if not, is a further €40 million, 80% of the total. The remaining 20% will be paid in stages, and will depend on certain targets being met. The total will therefore be around €70 million. If the targets are not met, Betis will continue to own that 20% or part thereof.
Presumably this last bit refers to them having the right to a percentage of any further sale
Marca and ABC have been spot on with this saga all summer