Comment by richardjs
Under $1000:
Voice lessons at the local community school of music. I'm a lifelong musician, but was an almost entirely solitary one. I taught myself different instruments, but I never felt like I could get to basic competency teaching myself to sing. I decided to spend ~$200 for a semester of weekly 30 minute lessons. (The community school cooperates with the local university to offer lessons taught by university students for a low rate.)
My singing improved (more work is needed), but the life-changing thing was getting involved with the local music community. It turns out they have a shortage of piano teachers--I had mistakenly assumed there would be plenty in my town! So I started teaching piano, which had long been a dream of mine. The school also connected me to local performance opportunities that are now a part of my regular music routine. And ultimately, the experience encouraged me to enroll as a (part-time) music student at the university, which itself has been extremely enriching and a tremendously positive community experience.
If I have a horrible voice for singing, do you recommend voice lessons? Just for karaoke and fun.