When it comes to paying for submissions, it does not matter how many you submit, though if you submit only a few from the site, i would call into question whether the other pages, have a chance at all of ever getting in the directory, due to picking up a flag, via the domain pages submitted. Though in another thread GeevesGuy suggests, that this is not the case.
Regarding what Lazer has said, certianly in a very long term view you MAY get listing in the indexes, though i would'nt place a bet on that. Certainly Teoma and Ink, are in the marketplace for paid for listings, so this free listings are hard to come by.
Regarding SPAM, no different pages tagetted at different products would not be regarded as spam, if they are very similar, but paid for, rest assured that the pages would be accepted, though one of them or several would be subordinate in a big way to, which ever the algo picks out as being the most relevant, so heading towards spammy (old style, change a couple of keywords, meta, etc). Is not worth the hassle. Better working with a themed approach that can cross in area's to capatilise on area's that one or many products may cover.