This
Amtrak blog post gives $110m for 206 miles of ACSES on the NEC, which seems to indicate around $500k/mile for the NEC. Accounting for single track on the Michigan Line that's closer to $150-300k/mile, so call it between $15m and $30m for the full 97 miles. In contrast, as of 2012
(Page 13) I-ETMS was estimated to cost $50,000/mile or $5-10m total.
ACSES is much more reliable, but it's a bad idea to install it in Michigan & Indiana unless Amtrak is willing to install receiver equipment on all of its Chicago-based P40/42s and the states do the same on the Chargers. It also leaves the problem of Kzoo-Detroit and Porter-Chicago, since NS will have to install PTC if the mandate stays in place - and they aren't interested in the high fixed cost of ACSES.