As a Landscape Architect in Austin I deal with tree replacement situations often. Most municipalities have set standards for Tree Mitigation required either for development or because someone killed, damaged or cut down an existing tree. It is different for every city, but generally it is based on species, size (DBH caliper inches), health of the tree, etc. The value of the tree will be determined by whatever the required caliper inch replacement will be. In Austin these would be classified as "Heritage Oaks" which must be preserved. They do not allow for live oaks of this size to be removed for development. Likely if they were killed here, the City Arborist would require a 3 to 1 caliper inch replacement. Hypothetically, you would have to plant & maintain for 1 year (90) 2" caliper category one trees to replace one 60" live oak. The replacement trees could be planted either on the original site or in nearby City Park Land. This replacement would be required in addition to a very hefty fine.
Two inch live oaks would be around $400 -$600 each installed including required planting soil, staking & mulch. This would put you near $90k for two 60" trees. I do not know the exact size of the trees in question, or the City of Austin's requirements, but with soil removal & replacement, Tree mitigation requirements, fees & fines you are looking at a very serious investment. The larger the trees you use for replacement the higher the price gets.
The guy is stupid and should spend some quality time in jail. Additionally, he should be financially responsible for the damage caused. Trees are not always "just trees". These have been around longer than many of the buildings on campus & are landmarks in their own right. It really is amazing to me that anyone would do something like this for a football rivalry.