That is a really good question.
I always find that when I need rope or cord I need either an awful lot or a very little bit.
100 feet of cord is not a lot when you start rigging tents or tarps. It is only 10 lengths of 10 feet.

I do have a few thousand feet of braided nylon masons line (100 lbs test) and a couple of miles of finer stuff like fish line, thread and dental floss.
(but I don't carry all of it with me all of the time, just a little bit of string and a pocket container of floss most days.)

I also like having lots of cheap string around too.
Plastic binder twine can be very useful and is dirt cheap.
A roll of binder twine is a lot of twine.

I have seen reels of poly rope thrown away on construction sites.
Poly might not be great for strength, holding knots or handling, but you can not get rope at a lower cost than that.

I don't buy Paracord because 550 is almost impossible to get here and is way over priced.
I get the stuff they sell to climbers instead.
Which reminds me to stop on the way home and buy a few more of hundred feet of it.