She was the only royal granddaughter to want a carriage drive through the town. They had to close streets so she could do this. She also opened up private areas of the castle and invited 1,200 members of the public to write in for tickets.
This obviously massively hiked the security bill. Other members of the family have got married in the chapel with minimum fuss and expense. She turned it into a public event, when she doesn't really have 'a public'. Most of them/us don't even know how to pronounce her name. I heard 3 different versions on the BBC and LBC yesterday.
Others have got married in the chapel in a much more low-key fashion, with fewer guests. The Queen has her own security wherever she goes. The extra cost was because they involved the public.
I think it goes back to Andrew's resentment of Charles getting special treatment as heir to the throne. Unlike Anne, he's always pushed for his daughters to be treated like William and Harry. He wanted them to be on the Civil List, have an allowance etc, with police protection officers.
Andrew and Fergie have always exploited the royal connection for personal benefit. (Andrew's shady dealings re money laundering over the sale of Southfork, and Fergie trying to sell access to Andrew for £500,000.)
I don't think either of their daughters really have 'a full-time job'. Anne and her family seem to have managed their royal status much better. It all looked as if she was trying to out-do Harry and Megan, when they'd made a point of scaling down from William and Kate. So, no, the whole premise of the occasion felt wrong.