let's find out exactly how you're going to set up this paysite - is it going to be the customer pays a certain amount and gets access to all the videos in the protected members area? that's how 95% of paysites work. simple.
or are you wanting to charge people on an a la carte basis where they can buy each video individually?
the first scenario is very easy - CCBILL takes care of all the password management. for affiliate tools you have scripts like Woj's that are fine and not expensive.
if it's the second scenario you'll need something like PhantomFlicks
http://phantomflicks.com 24.95 a month. or you could hire a programmer to code your own similar script - i've seen others besides PhantomFlicks.
you definitely don't need to spend anywhere near 5K