Finally back on my PC instead of my mobile
Here's a picture of what these "boots" refer too
They are rubber boots that protect and keep ball joints greased. I'm pretty sure there are 7 of these. 4 or 5 of them have been broken on my Jeep since I bought it used from day 1. I grease them from time to time but you need to be careful because the grease will leak out of the boot. I've had grease whip onto the inside of my wheels and unbalance them horribly until I cleaned them.
No idea how much it'd cost. You can DIY and save a bunch of money, you'll probably need a ball joint puller and an alignment afterwards. If you price it out let me know how it goes. I've been driving with mine busted for 2 years, I'm sure the ball joint wear has been accelerated greatly because of it and yes I do get bump steer and DW as a result.
Hope that helps! Post what you end up doing with them