For charting purposes they will not chart last sale price but...

For charting purposes they will not chart last sale price but either the bid or the offer. So for the spi index futures market you have two charts to choose from. To add to the confusion there is a further sense of unreality in that their bid/offer prices are anything up to 10 points away from the real market at any given time.
They in fact create a parallel, virtual market, to which they invite you to be the punter while they are the bookmaker. The spread is slightly more expensive than the equivalent broker's commission.
I think I prefer to stay in the real world.