What exactly are you trying to acheive by studying an instrument? Why did you choose to learn beyond hobby level?
Your approach sounds like you see it akin to training in a skill for a job. Spend the time and money on it and at the end you can play as well as 95% of people. But then you got bored/lost direction as you didn’t go so far as to do this as a new career so there was no end goal. Looking at the kind of money you think you need to spend, that sounds like professional level stuff (hint, a 40k piano will not improve your ability! But must be nice to play!)
It is hard, and not for everyone, to practice so much. I really enjoy playing the piano, but can never find the time or energy or drive to spend the time to learn to even a half decent level. Lessons would help me, but I’ve never found myself in a place to go for it. Which I accept. I’ll never play any Franz Liszt!
I don’t get the impression music is enough of a passion for you to get a lot out of ‘studying’ as you said you dont want to work part time to do so. So my advice would be to keep practicing and push yourself to learn new music as much as you enjoy it and maybe have some lessons to keep you on track . Maybe studying will suit you later in life, but not at this time.
You also don’t sound lazy btw! Like i said, it is hard work, especially alongside a job, but doesn’t quite sound like it’s rewarding enough for you.