We had a set amount when we started out.
When I cycled it seemed like there were very few OHWs. I was convinced it would take me 2-3 maybe more cycles.
DH and I agreed upon a set amount and that would be it. I was lucky, but don't know how my heart of finances would have handled it had I not been lucky.
I know people that have spent upwards of $50K to get their baby. Some have spent that much and still didn't deliver a baby. It's such a big huge gamble emotionally and yes, FINANCIALLY. Hands down the scariest, most risky thing I have ever done in my life.