Hi, I am new to all this, but help me understand this. If there is a crypto coin that is very useful and has functional value, not just speculative, say it becomes very expensive. What is to stop someone from just creating their own coin that is the almost identical to it, and using it instead, so high prices are not paid for the other coin? How can all these coins maintain high values, when people can just create as many new coins as they want?
You are correct, anyone can create a new coin, or fork existing coins. But doing so doesn't necessarily give them value. Remember that bitcoin price is defined by the rules of a free market (supply and demand), so if no one wants the other coins, it will have no value. You can actually see something similar with all these new airdops. People create ICOs and donate almost all the tokens, and no one trades them, and they just have no value.
Also let's not forget how the network is maintained. Miners would have to move to that new coins, or new miners would have to decide to run the full nodes for that new coin. If there is no demand for it, they won't do it.