I've done backtesting using historical options data on RUT that I purchased from iVolatility. The price was reasonable. But when I inquired into historical options data on futures, the price was about 10x as much! Why would historical futures options be so much more expensive?
Supply and demand? More people want stock/index options than FOPs. So if the cost of storing the data is the same for both you'd need to charge more for the data. Of course the cost is basically nothing to store data.....
Yes historical options data generaly is very expensive. I know CME Globex publishes FOP data for free in their daily bullentins available at ftp://ftp.cme.com/pub/g_bulletin/historical_data/ Have used these before then I did test some strats against the ES FOPs.