hard to say. No point in getting anything you don't like, no matter how good the deal. Then with the price/performance you could end up with a very cheap kava or even a very expensive one, if it is strictly bang for the buck. Finally, what good is a great bang for buck profile if it turns out to be too strong?
Price to strength ratio I would say realkava/kava kauai vanuatu. IIRC it is about $45 a lb and always strong. Soma batches have been a little nauseating for me while others are just awesome.
Consider shipping cost when doing comparisons. Some places have a minimum shipping charge of about $7. While some places have totally free shipping. So of course, that by itself, immediately saves you at least $7, no matter how big or small the order is.