I think that's a wise decision. It's not so much about underestimating a teen's ability to do something - it's concern about a teenager's often fickle interests than can lead to great expenditures on mom and dad's part thateventually get left in the dust because the child has lost interest.
My fiance's 20 year old neice "got"very enthusiastic regarding photography about 2 years ago. She has since lost adigital camera, broken one, and then losta digital video cam (cost her stepfather $500)and has now lost interest.
Also note that a less expensive "in between" camera can be passed along to someone else, so it's hardly buying something twice.