Is that really only 7,000? It doesn't look big but looks like more than 7,000 to me and that would be less than their current stadium. Seems like they're pretty smart. They know they're in football country and in this era making things look good is more important than capacity. There are a lot of basketball arenas seating right around 10,000. Given what indoor football practice facilities cost, $100 million seems about right.
There is no reason to build a huge stadium in Waco, just big enough for their fans to get the experience. They are not going to be able to pull any major NCAA events there with the AT&T stadium(Arlington) and UT's new $340 million stadium built by 2021 just 100 miles away to the North and South on I35. On top of that the AT&T Center(San Antonio), Alamo Dome(San Antonio) and the Toyota Center (Houston) is 200 miles away. There is no competition against those venues. Smart to keep it realistic.