Madrid sold them. Just the perception of their sales is completely different.
Here is one.
Club announces partnership with investment group Sixth Street as part of efforts to diversify revenues
Real Madrid has struck a €360mn deal with investment group Sixth Street and US sports entertainment group Legends to develop concerts and other events at its Santiago Bernabéu stadium and diversify its revenues.
...
As part of the deal, a new company will be set up to manage the stadium and the proceeds from the new business will be split 70 per cent for Real Madrid and the rest to Sixth Street. The agreement will run for 20 years.
---
Now what you won't hear in the media about the above is the penalties Madrid will have to pay for the stadium failing sound proofing and not being able to run any events for almost a year.