You can do the math a few different ways to see at what point it pencils out. I think by the time you have done 50 dives and are planning your vacations around diving, you'll find that it more-or-less does.
There will come a secondary question which is, which pieces to prioritize? I think that comes down to, which pieces of rental gear do you hate the most. For me, that was mask/fins/snorkel, then a computer, then wetsuit/gloves/booties, then a BC, then regs, then tanks, then a drysuit, then a better computer.
Tanks are the worst deal, you really have to dive a lot locally for them to break even, but you do gain some freedom, which to me counts for a lot. Avoid buying tanks unless you really value this freedom, or you really dive a lot within driving distance from your home. Conversely, if you never dive locally, then prioritize things that are useful everywhere and small: computer and regs would come before exposure gear, for example.