Actually, that's not quite right, because at the point the rotation starts you only have 5 full cycles to buy, plus the odd data pack - so that's $75 off straight away (although are you really paying $15 for them, I would have thought less if you shop around).
In reality, of course, you'd pick stuff up second-hand for much less (from all the whingers who are quitting, lol) and it may well be that my speculation of 10 deluxes is off-base. I would think 4 seems more likely (and is in-keeping with what their other LCGs have done in terms of one per faction). That would then mean the design team can concentrate on keeping to a release schedule that means the season rotation happens at a fixed time each year, as opposed to being delayed based on when product hits the shelves.
That also makes the design space about 330 less, which seems more reasonable. I know that makes for fewer unique cards than MtG, but bear in mind MtG has functionally equivalent cards in 5 different colours and functionally similar cards at multiple rarities - this greatly reduces the amount of design and testing they need to do.
I reckon the retail cost to get into the game by the time rotation hits will probably be closer to $700 - which is still steep, but also still nothing like what is required to break into MtG.