As explained in detail in a reddit post: This will be paid early access in the form of ‘Founder’s Packs’. The basic Founder’s Pack will cost $19.99, which includes access to the game, skins, boosts and other cosmetic items (all of which can still be earned by playing the game). 

The other Founder’s Packs, the Challenger/Master Packs which cost $59.99 and $99.99 respectively, will feature a greater number of skins and other cosmetic items, plus a Founder’s Pack to gift to a friend. 

Despite all this Epic Games stresses two things:

Paragon is designed in a way that players can compete and win without having to spend money. All heroes are free and cards can only be earned by playing the game. The only things that players will be able to spend money on are cosmetics and other in-game items that have no effect on the game play whatsoever.    Early Access exists for players to help make Paragon better by giving feedback and help change the game for the better. As a thank you to the players, the Founder’s Packs will get you in-game content for a significantly discounted price.  

So there you have it. If you choose to not opt in for Early Access, you can still sign up for the beta and play during the open beta that will take place this summer, free of charge. 

Paragon will launch later this year for the PC and PlayStation 4.