If you're in Canada, you are not an hour from where they ship (I don't know where you think they ship from?). ALL of the orders I have ever placed with LEGO S@H have shipped from the states and my most recent boxes say Southaven MS. That said, ordering on a Monday should get the parcels to you by Friday .. maybe Thursday, maybe Monday of the next week. You don't want to take that chance by listing something early, having it sell and then missing your shipping window.
Generally speaking, if you have to rely on ordering online (unless it's next day delivery) you won't beat the people who have a store 10 mins from their house. And then you have to contend with the people who buy _hoping_ to flip for a profit, and when that doesn't materialize in 2 hours after they've listed start dropping their prices.
Shipping in Canada isn't cheap so flipping these low cost items is also hard .. let's do some math:
$12.99 for a single.
+ 13% tax (I am assuming your in Ontario given your profile picture) = $14.67.
This little thing is going to be somewhere between $11 and $13 to ship in Canada if you print your label on eBay (that is still the biggest discount available, get yourself a free small business account so you can ship expedited at the counter). Do you have boxes already? Or are you paying for them? I buy boxes for bigger sets, try to recycle for little sets... boxes are from $1-$3 depending on where you buy (uline.ca has all kinds of shapes and sizes but there is no free shipping).
Let's say you list for 2x RRP and remember, online shoppers aren't going to consider your tax paid as part of 2x RRP.
$26 + $11 = $37. Whoa, that's almost 3x RRP now!
Let's assume it sells, and we subtract some fees...
$26 - ebay's 10% [$2.60] and paypal's 3% [$0.78] + their per tx [$0.30]... nets you $22.32. (you did list in Canadian dollars right? if you list in US, PayPal's exchange rate back to Canadian dollars isn't commission free .. they lie).
So now you've made a little money... $22.32 - 14.67 = $7.65 + $0.65 in VIP points. $8 is 54.5% profit for a fair bit of work... to double your money, you need to list at about 2.5x RRP.
NOW don't get me wrong, I am not saying don't try .. in fact, selling the poster could net you a few dollars more and that could be shipped in a padded envelope much cheaper (though they'll run you about $0.50 each if you buy enough). If you've never sold, it's good practice, might get you a feedback or two if you package them up really well.
But it's a risk .. what will you do if you don't sell them? Build them? Birthday presents? What a hassle to return them.. or hold them for 2 years while they appreciate and everyone else bought them for 30%+ off or during 2x VIP or during the mini beetle promotion which brought their original cost waaaay down and selling for 1.5x RRP nets them that 50% profit.
I know this is a little more general than just Brickheadz, but I think it illustrates why we sometimes chuckle and discourage people from trying to flip these things .. a few folks around here seem to have the magic touch to get these things from the stores early and most certainly they've made some cash, but unless you're expecting a shortage of Brickheadz availability (pretty unlikely with the smaller sets it seems) then it's high risk, low reward and most of us can't be bothered.