What is a reasonable way to determine the amount of mahr?

Hi, I’m a woman living in North America and planning to get married soon inshallah. My fiancé asked about the amount of mahr, but I’m unsure what is reasonable.

I come from a relatively well-off family, and my monthly expenses are about $4k individually, sometimes may reach to 5k (just rent and car expenses are about 3.5k, I know unbelievable). The cost of living is very high in my city and I have personal expenses too. I do have a job now, but I’m not sure if I’ll continue working after marriage, especially when we have children. I’d prefer not to rely on my family if God forbid, something were to happen. I’d prefer the mahr to be monetary because I believe it should provide financial security, in case something unforeseen* happens and I need to support myself until I can get back on my feet where I live. How can I decide on a reasonable amount of mahr?

Edit: *God forbid if something happens (as in health condition). It is not referring to divorce.