It's not quite that simple though bdw. The sums go something like this:
(Let's assume a flat costing $6M, 70% mortgage, or rent at $20K)
Buy
Capital outlay $2M (including taxes etc, yes I know I'm rounding slightly here)
Mortgage interest on $4M, about $8K per month
Management fees & rates, about $1500/month.
Maintenance etc: let's say $500 per month to make
Total monthly outgoings: $10K per month
Rent
Outgoings of $20K per month
PLUS you invest the $2M in something else and get, say, 6% return, which brings income of $10K per month
So net you are paying $10K
If the property market goes up then buying is better, if it goes down then renting is better, and if it's unchanged then it's a wash.
Obviously there are at lot of assumptions in there - tweak the values for your particular situation.