I've personally invested into an ICO back in the first quarter of this year. In fact, I managed to invest $100 in the presale of an ICO called Sapien. They have a beta right now and act like the decentralized version of Reddit. The incentivising of content is similar to Steemit, but with new staking methods and other tools.
My $100 worth of tokens bought me 1600 SPN tokens. I've received them and currently staking them on the platform. Those 1600 SPN tokens can be sold on Idex.Market for .00001 ETH each. So, that's about .016 worth of ETH. If I sold .016 ETH for $300 per ETH, then that would be about $5.00 USD. Even if ETH was worth $1000, that would be worth $15 USD.
My Conclusion from this experience: ALWAYS buy the ICO for at least 50% off AFTER they've been listed on an exchange. Do NOT fall for the lucrative technologies, marketing, and speculations.