I'm not real clear on how NIL money works, but Texas Tech just provided NiJaree Canady (college softball pitcher) about $1 million/year in NIL to transfer there from Stanford. That suggests that UT could get in the ballpark of a $200k minor league bonus offer without too much difficulty if they wanted to.
Out-of-state tuition at the University of Texas is $41,070. If Spencer isn't paying that (and he's not!), that's a quarter of the max the Phils could offer - before NIL is added. He's presumably also receiving room and board (estimated at about $15k/year). Add some NIL money. Add the long-term value of a bachelor's degree from the University of Texas at Austin (not insignificant), a shot at Omaha next spring, and a likely $25k MLB signing bonus next summer... If he were offered $1 million, yeah sure, but the difference between all that and $200k? Duh.
NIL changes things, probably more than we realize as yet. Of course, it also further clarifies just how dishonest it is to pretend that these people are amateurs, or really "student-athletes," at least in many (most?) cases. They're professional athletes, employed by universities as a side business (minor league athletics) to their stated educational and research missions.