You have to be doing much more than 100 RT daily to make leasing a seat a good deal, as you would not benefit from the Globex daily fee cap. The Globex daily fee cap on E-mini products is $50 (200 sides times $0.25). Your daily 100 RT is exactly at the Globex fee cap level. Because of FICA, seat leases only make sense if your average profit per trade is small. If your average profit per trade is large you are better off being a nonmember because the FICA tax ends up being higher than the savings from the lower rate of member exchange fees. A full CME seat currently leases for $3800 a month and an IOM seat currently leases for $1950 a month.
What if you set up an LLC and lease the seat in the name of the LLC and pay yourself via a K1. Won't that avoid the Self Employment tax?