This is basic supply/demand. Having an unlimited supply of product is not the same as their being unsold product on a shelf.
If demand is 10,000 units, and 5,000 are shipped, there's more demand then supply. The difference is significant enough that the price needs to be raised to reduce demand. If 9,000 units are shipped, it's still higher, but not as drastic, so the price won't change much. If 12,000 units are sent, 10,000 is still sold and 2,000 sit on the shelves. If 20,000 units are sent, the different is drastic enough that stores now reduce price to increase demand to move the extra 10,000.
I'm saying that demand from all players is significantly higher then supply on day one, but there's enough players like yourself that are not getting boxes on day one to make it so the difference will simply mean some people will have trouble buying packs/boxes in the first weeks or the store won't sell it for less then retail which will also discourage some buyers. If they shipped out an 'unlimited' supply immediately, the lower price point of 90-95 per box would hold. You'd then see an exponentially higher amount of boxes sold versus what is actually going to happen, and it's already going to be a large amount.
So, by there being less supply then total demand, it will inflate the price of the singles that are opened. Just because a ton of packs are opened does not mean single prices go down. It has to be more packs opened then players who want the card, so there is more copies of a card then is wanted.
There's also more players playing the game if there is that many packs being opened, which increases demand for those same cards and creates an equilibrium. No, that is not a hypothetical situation, there's a lot of recent 'quitters' and casual players that are coming back to magic because of this set, it's not just the Legacy/Modern fetch seekers and current players causing the spike in demand. In fact, the one thing I've realized from working at a store and coming from a competitive player's viewpoint previously, is that casuals (players/buyers/collectors) are a WAY larger group then most players realize. Like, they make up the majority of the market really. The sales of this set are being driven more so by casuals and players who never go past the occasional FNM, then legacy/modern fetch seekers, it's just they don't go post on the internet about it. I've lost count of how many times I've tried to explain why the fetch lands are even good to those players. They don't get it and many of them traded in all their fetches from the pre-release just to play more pre-releases or buy planeswalkers.