I think a part like this would cost a LOT more than $1500 per part.

The way it would probably be done in industry these days is to get
somebody like Scot Forge
http://www.scotforge.com/
to roll forge you a blank.
This would give you an oversize ring, without welds, that had the
grain forged continuosly around the circumference for strength.

Then, you send it to a machine shop that has a good sized VTL or VBM.

I was in a factory in Italy a couple of years ago that built big
machines, and they were making similar sized and shaped parts in this
way- a roll forged ring, machined on a vertical lathe about the size
of a two car garage. They had a whole row of these machines at work.

The material cost is one thing- but the real cost is in the equipment
capable of doing this size of work to these tolerances, and the
experience and infrastructure to support these machines.

This aint no garage job.

Like I said- If I seriously needed one of these, I would pick the
brains of companies that do it everyday, as job shops, and I would
start with Scot.