Why don't you tell her this instead :-

"Darling, I could buy you a crappy ring now and we can be happy. Or you can wait and I could buy you a tiffany few years down the road.  All I ask is for your patience at this moment."

For me, if you're gonna do something, don't do it half assed. Proposal in once in a lifetime.

But if you really can't afford it, forget it lor. No point killing yourself over a ring.

Either way, if you can afford it, you would've bought it.

Simple theory. I am okay to splurge. Others may not.

That's why we have this forum to voice out our opinions