Since I have retired, I have used my GI Bill to help pay for my CFI, CFII, MEI and 3 type ratings (Citation, 737 and 727). I have gotten in the neighborhood of $34,000 from the GI Bill. I still have 8 months eligiblity left - or about $8,000 to $10,000 in terms of aviation training.
I used tuition assistance while on active duty to cover my masters degrees.
I don't know all the current eligibility rules, initial costs, etc, but when it first came out, I had to pay $1200 to join it. Best $1200 I ever spent.
Just because you are a pilot or have a masters when you get out, it doesn't mean there won't be other job related training you might need or want. The GI Bill covers more than just college courses. It can be used for almost any type of training.