I have just had a chat with an EA representative. He was very polite and confirmed the 1€ was an authorization charge, and should be refounded within a few days.
He also advised me to use the Origin client for future purchases, since it "works better than the alternatives" and I'm not questioning that, but then I'd like to know why do 1600 BP cost 13.94€ in the Bioware store and 19,90€ on Origin. I'm not going to pay 10€ (Lair of the Shadow Broker is 800 BP) for one single DLC.

So, once the holding is cleared I'll try again with the Bioware store, and hopefully this time my order will go through. I'm very much aware that the Bioware support forum is littered of "I still haven't recieved my points after X days" threads, but as long as they provide me with a receipt I'm willing to wait the extra time.

I did have some problems a year ago due to some bug on their site but that got fixed and after that I had no problems buying the Bioware Points for ME2 DLCs. I don't really like the system becasue you can never get the right amount of points and you often have to buy more than you need but other than that it worked out well enough and I could play the DLCs. With ME2 you can atleast DL the DLCs so once that is done you can keep them on your HD.

I'm not a fan of the points system and would far rather just pay direct via CC or Paypal, but to address this point:

So far they've steered clear of this tactic. Every price point they have for their DLCs is covered by an equivalent bundle of points you can buy. So you never have to end up with leftover points.

Oh, so there are more bundles available than listed here?
http://store.origin.com/store/eade/cat/categoryID.46646100
I googled and the various EA/Bioware results all led me there. In case it's region specific: I can see a 800 points bundle for 10€, and a 1600 points bundle for 15€, and there are many different prices for DLC: http://social.bioware.com/page/me2-dlc
That would still leave the extra account and virtual currency, unfortunately.

Yay, more reasons to hate the stupid Bioware store system. I simply don't want to support this idiocy...

Yeah, I read that. I won't start to rant about Origin because I'm not really well-informed on that matter, and I don't really care about it either. I do not use it, and that's that.
I will miss out on some games, but then again I don't have much time to play them and have a backlog of other awesome games that will suffice for years to come. It doesn't really make much difference to me whether I do or do not buy EA/Bioware games, and if it's the same to them, well... good for them. I'm patient, and maybe they will release a super-ultimate-complete edition with all the ME games and DLC at some future point ;)

I've only bought points through the BSN where you access it from your Profile link (under your avatar), then 'Add BioWare Points', and it's been a long time since I bought any at all. Just checked it and they offer 4 different points bundles (1600, 800, 560, and 400), but I seem to recall they used to have more choices than that. Seeing how some of the DLC costs 320 points and 160 points, you'll definitely have some left over if you buy those.

So maybe they are pulling those bloody shenanigans after all. Bloody hell.

Alright, that still mitigates most of my complaint about that, since the 320 and 160 point DLCs look really superfluous to me.

@Avogadro6: I just realized: where do 1600 BP cost 20€? They seem to be 15€ in the Origin store for me. Still not buying them, though :D

Regional pricing. Also it only gives me the option to choose between 800 or 1600 bundles, while what I want (Arrival+LotSB) cost 1360.

Edit: to clarify, this is the italian page of the Origin store. The Bioware site offers also 560 and 400 bundles, and the prices in general are a lot lower there, perhaps even in line with the American prices.
Too bad that shop "isn't working very well" lately. Even Bioware reps are suggesting to use Origin instead.