The pricing would actually be buy 1 for $2 or buy 2 for $6, which makes absolutely no sense.
My point is that if your reading on a month to month, you're going to pay full retail per issue. But, if you're coming into the series late, comixology is giving you and incentive to go ahead and spend the more $$$ on a digital trade to save money. That's the way it is in most cases I have seen (trade is a better buy), but not so in this case I guess. Point, you can buy Rachel Rising 1-6 as singles on comixology for $11 or the trade for $10. If you spring for the single #1, you may not come back for #2. If you buy the trade, that's more $$$ for comixology up front. It just makes business sense to price all trades lower than what singles can be had for.