My best guess?
You probably gave $500 to someone on localbitcoins and that person charged you a 20% fee for the privilege of doing business with them, resulting in you receiving $400 worth of bitcoins in your localbitcoins account.
Then you sent those bitcoins from your localbitcoins account to your MultiBit wallet. In generating the transaction to send the bitcoins to MultiBit, localbitcoins charged you a 0.003 BTC fee which reduced the value of bitcoins received at MultiBit by an additional $1.20 or so.
When you made the localbitcoins purchase (a bit more than 24 hours ago?), the BTC to USD exchange rate was probably around $406 per BTC. Now, you are looking at your bitcoin balance in terms of USD today, when the exchange rate is at the moment around $390 per BTC.
Lets try walking through all this:
- You do a poor job of choosing a seller. You choose someone that charges 20% to do the transaction for you.
- You give the seller $500
- The seller uses the current exchange rate yesterday ($406/BTC) to convert $500 to bitcoins (resulting in 1.23153 BTC)
- The seller keeps 20% (0.24631 BTC, about $100 worth) for himself and sends you 80% (0.98522 BTC, about $400 worth)
- Localbitcoins charges you 0.003 BTC (about $1.20) to send the bitcoins to your MultiBit wallet
- Your MultiBit wallet receives about 0.98222 BTC (about $398.80 worth)
- The exchange rate drops from $406 to $390, therefore the exchange value of $0.98222 BTC drops from about $398.80 to about $383.07
The math works out almost perfectly. I'd suggest that in the future you do the following to save on costs:
- Choose a seller that charges a lower fee
- Meet with the seller face-to-face, and hand them cash.
- Have them send the bitcoins directly to your MultiBit wallet, skipping localbitcoins account and avoiding the localbitcoins fee
- If you are not purchasing the bitcoins for long term storage, then use them very quickly after you purchase them so there isn't much time for the exchange rate to drop
