I have a Brother 1034D serger that runs at least once a week for something or other - sometimes every day.
It's so easy to thread, I can almost do it with my eyes closed.
It has a differential feed for shirring or sewing knits, a rolled hem that takes two seconds to set up and is adjustable for a wide range of effects.
I trim my quilts before I apply borders or bindings. I made a 60" snowball quilt entirely on the serger for a new grandbaby. I finish the inside seams on doll clothes, pillowcases, all apparel.
I paid around $200 for it and it's more than earned its keep in the last few years.
Before I got a serger, I used to think it was silly to have this extra appliance - what would I ever use one for when I had so many good sewing machines which do everything?
But sergers are amazing - I wouldn't want to be without one, again.