a nice .org , The plural is registered of course , The Plural "Toxins" carries more value to an end-user buyer IMO, as it covers the whole spectrum of the "Toxin" poisons - ect. But at the same time, the google search results are very close for both. A poison control reference development would fit it well.
I am thinking $2,300 to $3200
It is a great .org, best of luck with it.