Now.. the issue of the taxpayer paying for the memorial is a tricky one.
I know the argument is that it brought business into the area and that this therefore brought money back into LA, etc...
I am not sure whether MJ paid for police expenses that occured when he gave speeches, etc... but certainly for his concerts the security and policing would have been paid for by him (or his company)
I can compare this in the UK to football matches.. when a football match is policed by the UK police then the football club pays for that, not the taxpayer.