As a rule you may need an Investor's Personal account in two main situations: when you plan to accept any other cryptocurrencies such as BTC, EOS and etc. in addition to Ethereum (ETH); and when you plan to conduct the KYC procedure (Know Your Customer). The price for an ICO Personal account depends on its functionality, the more crypto and fiat currencies you plan to accept, the higher price is. However, it is worth taking into consideration that an Investor's Personal account can cause additional safety risks as not only a decentralized and unchangeable smart contract appears there but a physical server as well which can contain potential vulnerabilities if it is not configured correctly.