Worst case scenario, you try the student testing, and if you don't think the results are accurate, you test again with the psychologist.
This could backfire, as you'd be forced to wait a year to use the same test.
We had DS tested via the university route, and in hindsight....I wish I'd shelled out the "big bucks". The tester was VERY inexperienced, and while they (student and overseeing psych) found DS to be the smarted kid they'd ever tested, his scores were not what I'd expected, and I think their inexperience is slightly to blame. DS was bored with the whole affair, underchallenged, the whole 9 yards. I'm sure the test would have been equally boring with a GT expert, but I expect the expert could have kept him better engaged, and his scores wouldn't have slacked off at the end.
I don't know.....you could get lucky, but it is a risk. Hopefully you'll get some satisfaction with just the Explore!