I hesitated for years about buying Roxanne's Glue Baste-It in the EZ Squeeze tube. After all, I had Elmer's washable white school glue on hand and it worked pretty well. Finally, after several years, I splurged and bought it:
https://www.amazon.com/Roxanne-Glue-...dp/B0089O3696/
It sat unused for awhile. At that price, it was like the "special" gifts that get put away in drawers for years because they're too good to use. Now, however, I'm working on a quilt that requires precise piecing and I decided to try it. Wow! What a difference! It really is easy, and I have absolute control over glue placement (and can get tiny dribbles).
The other tool I thought was pricey when I purchased was the Slidelock ruler:
http://www.quiltersslidelock.com/purchase/
I splurged on the 3-piece set and use them all the time. I could live without the flat ruler, but I use both sizes of the gripping ruler almost every time I have anything to cut. Aside from helping me cut straighter by holding everything in place, I consider them insurance against a visit to the emergency room because they keep my ruler hand safe.
I should start another thread about tools that were extravagant and did not work out -- such as the large, plastic Martelli machine binding tool collecting dust in a box near my desk. Looked great when I saw it demo'd at a quilt show. I see they don't sell it on their website anymore. That's undoubtedly a good thing.