don't get caught up staring at the percentages; they have to add up to 100, so just because something is 75% doesn't mean it's bad, it just means that's where work was performed compared to other steps.
i put more importance on things like the estimated number of rows inserted being 19213 and the estimated subtree cost being 87.8014 than anything else.
you said it inserts one at a time, but this looks set based.
can you obfuscate the insert statement and show it to us? the actual execution plan would tell us everything, if you can post that.
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