In a word: EXTREMELY.
I recall hearing a broadcaster at the College World Series several years ago say that of the 200 players present, only 2 received full scholarships. How he knew that is hard to imagine; but, he said it. I've certainly not tried to corroborate it.
There's a webpage on this site (I think it's in the recruiting section.) that speaks to the issue of "scholarship blending." It lays out the several requirements specified by the NCAA.
In a nutshell, it's generally difficult to "blend" the two (except in states that offer "Hope-type scholarships). The principal "kicker" is that whatever is given to the player in the way of academic money has to be equally available to non-student athletes for it to be excluded from consideration as "athletic" money.