Do they actually contribute massively to the economy?
Don't know if that is massive.
Do they show there data anywhere? Is there any peer review? Who commissioned that report - what conflicts of interest are there?
Meh
https://www.independent.co.uk/news/business/analysis-and-features/royal-wedding-family-how-much-uk-economy-benefits-cost-meghan-markle-expense-a8345436.html
@NotThamesWater started
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Don't know if that is massive.