99% of the spiders that will visit your site - will themselves take up 10 times more bandwidth than the traffic they drive, after they include you. :)
Keep in mind, if they don't have a nice db to saerch, then - nobody will want to use it, which means nobody will pay, etc.
It's a catch 22, and the reason PFI is a *failed* business model. There isn't one company yet that has proven it's sustainable, even for a few years.
Inktomi, the author of the idea, has already sold out. AV & FAST, the two other engines that followed suit, have been sold as well.
Ask / Teoma is the only one left that has a program & is still independent, but if you look at where their revenue is coming from it's their partnership with Google for Adwords placement in the SERP's.
Nothing about PFI is driving their revenue.
So imho, don't pay, and eventually, the search engines will include you. Like I said, it will take between 3 and 4 weeks, usually, from the date of first spidering.
Yahoo links help placemnt, as do DmOZ links.