The MBoM is available once more at the US lego.com store. 
If you wanted it, get hopping, because they run out quickly. Purchase over $75 dollars of Harry Potter legos and it will automatically be added to your cart. In addition, they've extended the offer for either the Fire Helicopter or Police Water Scooter lego City Polybags, you can add them to your carts for free. (Use code
FR29 for the City Fire Helicopter or
PC29 for the Police Water Scooter at checkout.)

Nifty. Now let's talk
lego arbitrage for a moment. First and foremost,
make sure you're registered as a lego VIP user. It's free and it gets you upwards of five percent of anything you spend off your next purchase. There's virtually no effort involved, the points are good for about a year and a half, and even if you have no purchases planned, it doesn't hurt to do this 'just in case'. (Plus, there are freebies. I got a snazzy keychain recently. Most satisfying. ๐)
Next, even if you have all the HP lego sets you wanted and didn't care about the MBoM (๐ฎ it's okay, we can still be friends), selling the MBoM on ebay in the states currently nets you upwards of $40 (as long as it isn't an auction <- do NOT go to auction atm).
Set a price or best offer. You may need a bit of patience to find a buyer depending on the price you set, but you can place up to 200 ads per month for free, so it doesn't cost you anything but patience to wait. When putting your order together, you should also consider the average prices of lego sets in stores, or sets that are only available at the lego S@H and select wisely. For example,
40419, the Hogwartsโข Students Acc. Set, is $15 on the lego site and often sells for over $20
on ebay. (Here in DE, it's only available at the S@H, ebay and amazon marketplace, which drives the price. Check your country by googling availability.) That right there means five student sets for $75, completely resold at present rates, along with the MBoM nets you upwards of $65 profit on ebay (and you can throw in the City poly bag, too). Ebay will charge 10% of the
"final value" in fees (note: without an ebay shop, that includes shipping and handling). Hanging on to the sets and doing this at a later date almost always gets you better prices, too, but this model is if you didn't want to sit on the sets for any length of time.