Monero has lost ~90% of it's value vs. BTC since last September
Uh, no. You are misreading something.
My bad, I was looking at the market cap valuation which is off that much. The BTC price is only down ~75% from last Sept. Still not exactly great price performance....
http://coinmarketcap.com/currencies/monero/ (click on "all" for the full history)
There's something buggy about coinmarketcap.com's XMR charting. The "All" chart only goes to Feb 15, before the recent increase in XMR price. For a better price chart, see: