Hi,
I was a National Merit Scholarship Finalist and got a scholarship from it, back in the day (1984!) Back then, they didn't have the writing section, so they doubled the verbal score and added it to the Math score, so the numbers are comparable, sort of...
I got a small University based scholarship to the school I wanted but it was only $500/year, so $2000 total. The real benefit to being a National Merit Semi-Finalist was in the prestige of the program and getting schools to recruit me. I think it helps to get some leverage with the school of your choice if they know they are competing for your high achiever. I ended up getting a very lucrative merit based scholarship at my school of choice.
It was also fun getting offers from schools all over the country recruiting me with scholarship offers included...a few were full ride offers! Some schools offered expense paid trips to come visit.
BTW, I only had a 195 score...the cutoff in TX last year for semi-finalist was 217, so the competition is WAY stiffer now-a-days.
My freshman daughter just got her score and it was 195, which is great but we still have work to do to qualify by the time she is a Junior. I found last years state cutoff info on the web. Each state's number is different.