Fees million at most. Real estate + connections are commoditized - tens of thousands a month for starting out.
I couldn't find any reports of prices that low. According to one article, at least, Spread [1] charges ~$300k a month.[2]
[1] http://spreadnetworks.com/network-map/
[2] http://www.motherjones.com/politics/2013/02/high-frequency-t...