I guess you should also consider that VRRP is optional. A minimum of 2 IP addresses is mandatory (one of each MX). Also of note is that if you don't use VRRP that the IP addresses don't have to be from the same ISP circuit.
You could use the primary circuit on the primary MX, and a cheap consumer grade Internet circuit for the secondary MX.
ps. I only enable VRRP on about 25% of the installs tat I do.