I bet this this website cost London £100k or more. They probably contracted it out to some supplier to build and maintain, and they are charging through the nose for hosting it, because the people on the London horticultural team don't do HTML. While I applaud the effort, I do wonder if it is tax money well spent. Perhaps a spreadsheet on a shared drive would have been better value for money?
Tbh I feel like that's probably an underestimate, but otoh that's probably a fraction of the cost of maintaining the trees themselves, so I'm not sure it's worth fretting over.
This is therefore a reasonable expenditure of some government resources. Just as when they paid "Royal de Luxe" to perform The Sultan's Elephant over several days. The Sultan's Elephant is street theatre, an enormous mechanical elephant, a giant little girl, and some other apparatus turns up, the puppeteers from Royal de Luxe operate these puppets to tell a story for the entertainment of just... everybody who happens to be there, it's on public streets, it's not ticketed, it's not in some arena or screened off area, it's just in your city where you live and/or work. Perhaps you came specifically to this part of the city to see the giant little girl, asleep so peacefully, or perhaps you were surprised to find your journey interrupted by an enormous elephant walking down the street when you went to buy lunch, it doesn't matter, this sort of street art is a reasonable investment.