Everyone selling big amounts of goxBTC at the moment is arbitraging. You can easily make 50% in just a few hours by doing this:
1) Deposit into Gox via OKPay - it takes a few hours to clear.
2) Buy goxBTC
3) Sell goxBTC for "real" BTC at 0.6ish while the real price is 0.4
Example: at $250/goxBTC, for $10,000 you get 40 goxBTC, you can sell them for 24 realBTC. 24 realBTC on stamp at $625 equal $15,000.
4) You can send the real bitcoins back to OKPay and get ~$15,000.
5) You now have $15,000 to buy more goxBTC with.
Rinse and repeat and it's a money printing machine, a pretty fast and incredibly profitable arbitrage.
Prices are going down because there's a lot of competition between people doing this, so the market corrects itself.
I don't see the hour to deposit to Gox via OKPay, how is that doable? Do you send directly to mtgox wallet from OKPay?
This is a horrible idea right now. I am waiting for almost 24 hours from okpay to gox now, support only says it will take 24-48 hours and I have to wait. Just hoping I get it before the press release tomorrow or I might be GOXXED again. But maybe that is what I deserve with this name