Marketplace assets are third-party content (art, sounds, code plugins) sold by other developers. You are never required to buy them. UE4 includes free content (starter content, Paragon assets, Infinity Blade packs, etc.). If you want to “fix” the perception, remember:
Sometimes, people aren't asking about the price. They are asking a technical question: "How do I fix the 'Unreal Engine is not free' error in the launcher?" Is Unreal Engine 4 Free Fix
Unless you are an indie developer hitting the jackpot with a viral hit, Unreal Engine 4 is effectively 100% free. The barrier to entry is financial zero; the barrier to cost is financial success. If you want to “fix” the perception, remember:
under standard terms. The only cost is a fair 5% royalty after your game becomes commercially very successful (>$1M gross). For 99%+ of developers, UE4 costs exactly $0. under standard terms
If you encounter a paywall or licensing error: