I can't explain why dogecoin is worth so much, probably just crazy speculators (after all, the only market is people using it as a joke/meme, no one is ever going to spend significant amounts of money on it - I hope.)
But yes you can create your own cryptocurrency and make a lot of money off of it. This is a good and a bad thing. Good because it should create competition to make better cryptocurrencies. It also helps build the currency as all the miners invest resources in it and get exposed to the currency and have an incentive to try to get others to use it. Bad because, well that money is coming from somewhere, and the users of the cryptocurrency are essentially paying a tax to the miners for not really contributing anything of value.
Except it's conceivable that having virality baked into it (e.g. being a "joke/meme") could actually help its adoption move much faster than it otherwise would. And once you have a cryptocurrency that has a lot of buy-in, why not use it for real transactions?
I'm not ready to say DOGE will win the cryptocurrency wars, but it certainly wouldn't the first time that a "joke" or "hack" turned into something real and lasting.
But yes you can create your own cryptocurrency and make a lot of money off of it. This is a good and a bad thing. Good because it should create competition to make better cryptocurrencies. It also helps build the currency as all the miners invest resources in it and get exposed to the currency and have an incentive to try to get others to use it. Bad because, well that money is coming from somewhere, and the users of the cryptocurrency are essentially paying a tax to the miners for not really contributing anything of value.