Problem with that 40-50% discount is I don't know of any LCS that has the volume that DCBS and Midtown have to qualify for the same discounts. Also, since DCBS's online store is a preorder-only service and you prepay for your items (typically around the 15th of the month prior release), they don't carry the same risks of unsold product that a normal LCS does.
Maybe the LCS can offer a preorder service similar to DCBS and Midtown's so they can offer bigger discounts. The LCS makes a smaller profit per item but that profit is guaranteed and carries no risk as well as providing advance revenue to help with cash flow. That said, given rent, labor, etc, are fixed costs, they might need to make up for the lower margin with higher volume.
My LCS has a preorder program like this and they give all preorder customers 30% discount off DC/Marvel and 20% off on all other pubs. Discounts are regardless of order size so whether you preorder 1 comic or 50, you get the same discount.
I've approached 3 different shops in my area, none can even offer what you describe. If they did I'd have to consider it closely.