Ended up going to the local surplus store today and scored 300' of 16C ribbon for $15 Wish I had the money to buy all they had, there were around 5 more rolls there. Anyway saved myself a bundle, it would have cost around $75 for all the 16C and 6C cable I needed. I'm just gonna unzip 250' of it to get my 6C cables. Unfortunately half of them won't have a polarity stripe, so I'll have to be careful when assembling the cables.
Now I just gotta find a place where I can get IDC connectors cheap and fast. I need 100 6P ones and 100 16P ones. I'm thinking about using half direct wire to board ones for the 16P so I don't need to buy a bunch of matching shrouded headers. Stupid things are expensive!