Possible round worm infection

Hi all!

I have 5 cats, all rescues. I woke up a few days ago and found what It looks to me like roundworm? However I don’t know which one of my cats threw it up.

I knew I needed to take action immediately and couldn’t afford dewormer through my vet for all 5 cats (was quoted over $200 for a box of 6 single dose treatments, and they would need multiple doses, so multiple boxes). I instead ordered panacur or fenbendazole on amazon and all of my cats were treated for 3 days. (Panacur can be used off label in cats) Oddly though, I’ve never seen any other signs of worms, and no other worms have come out of any of them after treatment.

I was doing research and apparently a cat throwing up a worm is a sign of a bad infection however i literally only seen the singular worm in the vomit one time and nothing before or after that incident so im confused, and possibly looking for other opinions on what this means.