Coinbase is a major exchange, they make money on volume not by scamming. Follow up with customer service, I suspect they will be willing to help.
Also, just a note, you might be surprised at how easy it is to make money if you just buy when everyone is selling, and sell when everyone is buying. These markets are massively volatile, and change every day.
NEVER, under any circumstances, make investment decisions when you are feeling emotional. This pretty much guarantees you will lose money.
Never put more than you are willing to lose in to any investment.
If you do not feel confidant enough to hold an investment long term, whether or not it drops in price, you should not buy it to begin with unless you have significant knowledge and experience with short term trading. Generally 90% of people who trade short term lose. Are you good enough to be in the top 10% of traders? Most likely not.
Investing is a tremendous amount of work. If you don't put in the time, you will lose.
Because I want to be specific and hopefully prevent people from losing everything, I will give a specific example. The most recent price I paid for bitcoins was ~3100$. But very shortly after I bought, the price went as low as 1800. However I kept an eye on events, and I decided that the drop was only a short term blip due to certain events (it was FUD). So I held because I was confidant that I wanted to hold those coins long term. I am still holding. Ok it was only 1k usd worth but still, the point is that I knew what was going on and was comfortable that long term bitcoin was a solid asset. If you can not make this sort of assessment, then do not buy. You are only putting money in to the pockets of those 10% who know how to play the markets.
How stupid can you be? OP is clearly being fleeced by the exchange and your reaction is to moralize that he shouldn't have sold to start with. One might think you are working for a scamming exchange to address the problem in this way