I wrote a piece in spanish on this subject a few days ago, including revenue calculations and customised for Spain's taxes. Just uploaded it here:

https://yakihonne.com/article/naddr1qqgxydee893nsvpc8qmkgdesvserjq3qn92k2pexqfruaftud38adcxmmtfwk6u2eym69hq3xe09efk0tsyqxpqqqp65w2hpl74