The time component of making cables is very often overlooked.
For a hobbyist it's not normally a problem spending a few hours finding the connectors/cable/wiring diagram and physically making the cables, but when time is money, pre-made cables are cheap.

All my servos have been bought from Gary/Zapp. Certainly not the cheapest option, but he's not just a box shifter, and should you need any advise, he's only an email/phone call away.

One thing to bear in mind, is servos should be inertia matched to their load for best performance. Too big or too small a servo for any given load will not give a good tune. The spindle on my mill demonstrates that perfectly. It's a 110 frame medium inertia servo, and the best positional accuracy I can get before things go unstable is about 200 encoder counts, as it's not got enough of a load to help stabilise it. My lathe on the other hand, which has small inertia 60/80 frame servos, holds sub 20 counts without any problem, as the servo load is a good match to provide stability.