I am now starting to see what the main issue is with these cryptocurrencies. It seems that it is very easy to buy them with "hard" currencies (such as USD) but there is a real reticence to sell the cryptos back to USD.
You are incorrect. It's easier to sell cryptocurrencies than gold. You can sell them at almost any exchange (GDAX or Bitstamp for example) for a fee of around 0.25% (less if you trade high amounts), plus the BTC transaction fee of around five thousand to fifty thousand satoshi depending on what you choose to pay. Selling gold is very difficult to do at the spot price, especially when trading large amounts, but the BTC market is very liquid and it's easy online.
All assets that you hold are subject to capital gains tax when converted back to fiat, which is the only other major fee except for the ones that your bank charges you. This includes property, gold and anything which doesn't lose value every single year on banks' whims. It has no relation to HYIPs/Ponzi schemes because BTC exchanges are not a central entity. The fees are not set by BTC, they are set by exchanges, banks and governments (and the fee market for transactions, but that's only a small amount from a traders' perspective).
It's very simple. Trade on a major exchange (
GDAX,
Bitstamp) and take their 0.25% fee. As for other fees, that's your fault and you should have considered the laws of your country before getting involved.
If you want to trade P2P and don't like centralised exchanges, you could try
LocalBitcoins instead. That's for whatever fee the market sets, if any. Typically you will sell at a premium over the normal exchange rate if you are a trusted seller, because people often prefer to buy P2P.