The next cheapest 1/8 GT8e I know is the Exceed Mad Drift, though they sell out fast and take 6-8 weeks between re-stock:
https://www.nitrorcx.com/18driftcar.html
Remember, you get what you pay for, so don't expect race grade quality but here's a review of this car to get an idea of what to expect:
Just to clarify, are you still trying to hit a speed run of 100mph???
If so, that's going to be extremely difficult to do with any 1/10 platform.
Regardless, I would consider the GT8 class. Another option if you want to cut costs is to convert a 1/10 4WD SCT which is essentially the same...