unless the other debts owed by BioAmber would be settled, then the price should be much much much higher
You might have that backwards, if I'm understanding correctly. If the debts were settled, (they weren't) the purchase price might have been higher, or the actual company could have been included.
But, I believe the main reason the purchase price was a mere $4.34m, is due to the fact that the plant and company were operating with such huge losses. No one wanted to pay more for something that wasn't working very well. Does that make sense?