Well yeah the M3 Slot-1 will be a sweet deal . but the price thing isn't M3 Team's strongest point . Looking at the price diverence between the M3 and supercard. But some things might get cheaper because of the smaller packaging needed.If everything goes as it should the M3 team will be ruling this chart. With thier own Micro SD Slot-1 card.
And from then the chance of a G6 Slot-1 being introduced will get bigger and bigger.
The price difference between the M3 and the Supercard was mainly because the M3 used good quality internal memory for GBA games. M3 versions without GBA support are much cheaper.
The supercard uses a low quality memory chip so GBA games have slowdowns and bad suport.
In a slot-1 solution there is no such memory chip