MaizieD
Where do you think that the money that is spent on it will go? It's not a bottomless pit or a big black hole. it will go to paying people or businesses.
Let's think.
Start with the military,;all those ruritanian uniforms have to be maintained, kept clean and polished. I doubt the military maintains its own dry cleaners, nor does it produce its own cleaning materials. The splendid horses have to be fed and shod, horseshoes don't materialise out of thin air, neither does feedstuff (as I know from experience!), someone somewhere supplies them for a price. Then there's the saddlery which has to be repaired and kept in a safe condition. Does the army have its own leather workers and where does the leather and thread come from?
Let's not get sniffy about souvenirs, they're all employment and a source of income for people and businesses (though I hate to say that it might mainly be Chinese people and businesses).
Hiring barriers, hiring toilets, hiring transport to bring in the extra police, security etc. Transport and catering for people coming into London to watch the spectacle, printing orders of service, clearing up afterwards...
I don't know the half of where the money goes, but be sure that it all goes somewhere and it will circulate in the economy and mostly come back to the Treasury via taxation. Because that's how an economy works.
But, as I say, despite this potential boost, the optics could work against it because people don't think it through.
I'd be interested to know just how much benefit to the economy there was from the Queen's obsequies.
On the other hand, I agree we could do without wall to wall media coverage of it... 
I'm probably being a bit thick here, but aren't all those things paid for by taxpayers in the first place, so how does that equate to "profit" when we spend millions on them and get back a small percentage in taxes?
One of the biggest costs will be on security for the thousands of VIP's attending and massively increased policing costs. How does that taxpayer money come back into the economy?