Security in decentralized applications is a must that has to be carefully dealt with, since we are dealing with real money from real people that trust the code to be secure enough to keep their funds safely. You can't skip security analysis in your code, because otherwise you'll be risking people's money, so it's a huge responsibility.
That's one of the main reasons securing a smart contract can be so costly in time and price. Audits, bug bounties, and code analysis are common for ICO smart contracts and those that handle real-world funds. They are naturally expensive because they require careful consideration of all the moving parts in a smart contract.
