Okay let's clear up what a "fair" price for XRP is.
XRP is a different beast, because there is a limited supply, but you still get fairly natural markets, especially the BTC/XRP one.
http://webr3.org/apps/xrp/charts/btc-xrpTo get a fair price, you want to look at the depth of the market, the price at 1,000,000 XRP on either side. Currently this equates to 5700 on one side, and 7000 on the other side.
The middle of this is 6350, then traditional secondary market sales would be circa +/- 5%.
So if you're buying XRP expect to be getting ~6030 per BTC, and if you're selling XRP expect to be getting 1 BTC per 6660 XRP.
Anything between that range is a very good deal.
Obviously in reality there are other factors, such as the general trend of the market, and whether there is more weight on one side than the other, but for a fairly evenly spread market, the above is a good way to approach a deal.
Hope that helps.
