The thing about some of the rares/epics you get in the starter pack of each faction is that they are either relatively easy to get by trading (since they are less needed or more common than others) or simply not that needed for the faction to run (I'll take 'The Dragon Project' as an example for this case).
50$ worth of boosters is...well...about 25 boosters. That's 375 cards, you'll get some spares to trade for specific rares you didn't get, and you're more than likely to have the basics to run any faction.
You may be right though, I never did buy any starter deck (or maybe only the one).
I did some working out last night to see which is the best option
$50 (not including the bonus IP) allows you to get the collection pack plus 18 super boosters giving 308 cards (at least 20 rare, 1 epic, 1 legendary). or the Collection pack, 5 starter packs and 6 super boosters giving 343 cards (at least 18 rare, 6 epic, 1 legendary).
looking at the starter packs most of the commons/uncommons are gained from the campaign (though maybe not 3 of each).
So I'm thinking I will spend it all on super boosters and use the bonus IP to get one or two starter packs depending on what rares+ I get and what faction I will mainly use/epics needed. Or just get another 4 or 5 super boosters
The decision now is whether to get core or rise and how many of each.