Post-negotiation offer--did I leave money on the table?

I interviewed for this company and received an offer from them. On Glassdoor, it suggested that all their assistant-level roles pay the same amount. I wasn't sure if this was negotiable or not but that amount was just so low, I didn't think I could do it for the COL of where I am so I went for it. I'm not the most suave person; I asked if that amount was negotiable. The recruiter told me that was the base salary that all their assistants start with and asked if I had a question, almost seeming to prompt me to negotiate (but I'm unsure if I read that situation correctly). I asked for $2,000 more (was worried about scaring them off if I went too high), and she came back to me with even $1,000 more than that. Did I undervalue myself?

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