When we initially began the Paladins beta, our general plan was that the game would contain a relatively small number of champions -- with each champion having a very large number of cards.
As we have progressed with the beta, it has been clear from your feedback and our own experience that most players prefer to have a larger number of champions, each defined by a basic playstyle and purpose that is enhanced by the cards. In this new scheme, there will still be a good number of cards per champion, but not as many as initially envisioned. (At present, we are thinking there will be around 20 to 25 cards per champion). In addition, we have made it much easier to get cards and to craft cards you desire for a specific champion at a specific rarity level.
Right now, we are working hard to significantly expand our champion roster -- in a manner similar to what we did with Smite (releasing new champions on a regular cadence for hopefully a long time to come).
With this new system, we have decided to also make a change to how champions are unlocked. Players will now need to unlock champions either with Gold (earned through playing the game) or Crystals (purchased with real money or earned during promotional events). The price of each champion will be quite reasonable and relatively easy to earn through gameplay (very similar to Smite).
A set of 7 characters will always be able to play for free by everyone. This list of 7 characters will regularly rotate, so that players that don't spend any gold or crystals still get a chance to play every character for free on occassion.
You will be able to try all champions in a practice mode prior to unlocking. And we will also add a way for you to "rent" a champion for a very small gold amount to try out.
As a reward to our early beta testers, anyone that has played in the beta prior to when this change goes active will have all of the champions released up until that point given to them (no need to purchase).
I'm extremely excited about some of the new champions coming to Paladins soon and look forward to seeing you in the Realm!
UPDATE: Current plan is for champions to cost 10,000 Gold or 200 Crystals. To buy all the cards for a champion typically costs between 5,000 and 7,000 gold (although you can also get cards through chests as well, which you can obtain through different ways).