Well, this does not address one of his core argument, which is basically coding for average Java developer is just one small part from his/her day activity.
Especially in the case of maintenance of existing legacy system, where most of the activity resolves around understanding existing code, writing is just a small part of it. If maintaining the system needs to be financially feasible, hiring expensive Scala developer may not be the best idea to maintain the system. Unless of course, using Scala outweights the benefits of using Java even with the potential financial cost.
Especially in the case of maintenance of existing legacy system, where most of the activity resolves around understanding existing code, writing is just a small part of it. If maintaining the system needs to be financially feasible, hiring expensive Scala developer may not be the best idea to maintain the system. Unless of course, using Scala outweights the benefits of using Java even with the potential financial cost.