Why is the price of plain white vinegar going up so high?

I was in the grocery store the other day and noticed that a gallon of white vinegar has gone up to $3.97 - I bought vinegar earlier in the summer and it was expensive then but I *think* it was only $2.99 if memory serves. And that was higher than last year (when I could have sworn I got it for $1.89 a gallon) Shouldn't plain vinegar be inexpensive?

I've tried doing web searches and can't find anything about it. Does anyone have any idea why the price is going so high? This is more than milk!

Thanks for any insight you can offer!

Tina