In an earlier comment, I claimed rapid advances in wind technology had significantly cut the cost or increased the value of new kit versus old. The article below goes into the capacity factor economics of larger turbines and taller towers - up to 140 metres.
The windfarms in the US business Infigen sold are on average over 10 years old. Measured against the new, they are sorely dated and were therefore heavily discounted at sale.
Infigen has made clear they intend to build a number of the 'shovel-ready' Australian projects already in hand, subject to finance. These are likely to be highly profitable, relative to older windfarms.