Doing what I should have done long ago, I waded through my shop...appraising my equipment. Listing what I paid for each, what my bottom line would be if I had to sell them, and what I would want to get for them. For instance, my DJ20 jointer: Paid $400, but a Byrd head on it for $300, and a mobile base for about $100. So, I PAID $800, could easily get $900 to $1000 for it, but could probably get $1200 from the right buyer.
This, after going through my entire shop, made me realize which machine I had the most "in". And I was kinda surprised. I wouldn't have thought it before I started buying equipment. For me, it is my lathe. A 1981 PM90. Now I bought it for $300. 3 phase converter $145; poteniometer, reverse switch, and box for those two things $50; digital tach $100; risers (to make it an 18"er) and other stuff (not including tools for it) $350; paint and refinishing materials $50.
So, for me, it is my lathe at $1000.
New or used, what is yours? You don't have to say how much you have "in"...
EDIT: Sorry, I could only list 10 options.