I would spend more if it was someone I knew had a good reputation. Often there is a lot of behind the scenes stuff meant to manipulate SERPs. On the other hand there are site that have a high pagerank AND have a ton of quality traffic that fits the niche. That is different story. So if it is a directory, I would want to be able to see how they got the high pagerank, and what the likelihood of me getting traffic would be. That would help me establish a price. I have a few links on a pagerank 8 directory now, and I don't get any traffic (maybe a couple per month). There haven't been any serious google pagerank updates since April, so no surety that the link will help my pagerank either.
I do not like paid submission. I like to byu blog post on other's blog to control the quality of the link..
Assuming the page rank is legitimate and assuming the categories actually have some rank too, I'd still probably not pay to submit because if you are promoting a directory solely on it's PR, it's probably sooner or later get Google slapped anyway.
Yeah, its amazing anymore checking a site's backlinks and seeing that it was about something 100% different a short while back.