The charges should be exactly the same on the order page at gog.com, but of course if your bank/card issuer has extra charges then those will be added onto your bank statement/receipt.
The price looks strange though. Which two games did you buy and which promotion are we talking about ? ( The interplay 2 for 1 or a previous one ? )

The interplay promotion - i bought freespace 1 and fallout 1; I just checked the order email again yep it says 5.99

The price was strange, as Kylling said. The only advice I have, is that you contact your bank and GoG support. They'll probably be able to tell you more.

$5.99 in USD is currently $8.60 in NZD, which is very close to the number you just gave. I'm pretty sure the credit card transaction is showing in NZD. And I'm pretty sure that you'll kick yourself if I'm right about this.
edit: I'm also in NZ; I've made some GoG purchases recently and none of them have had any mysterious extra costs

i was typing the same thing here.
it's just a conversion amigo.
no more no less :)

What he said :) Be a good thing to check out if its your local currency

It looks to me like there may be a bit of a misunderstanding here. The prices GOG lists is 5.99 US Dollars, which when converted to NZ Dollars works out to about 8.60 with todays exchange rate. Obviously the exchange rate on the day of purchase may have been slightly different. Add in a small charge of say 3 or 4 percent for currency conversion by your bank (theiving sods that they are) and you will get somewhere near your figure.
Edit: Fiddlesticks, I need to learn to type faster. What they ^ said

Sorry if I sound stupid, but...that $8.92...it's still in the US$, right?
Edit: Beat'd. I'm slow...

[url=]http://www.xe.com/ucc/[/url]
Above is a currency converter. I recommend bookmarking it for future reference as it comes in handy when buying through the internet.

Well silly me - I did check their policies on pricing in advance you know ;->
What are your prices in different countries?
Our prices are always the same, worldwide. It doesn't matter whether you live in the sunny Bahamas (lucky you!) or some place where polar bears roam the streets, it's always $5.99 or $9.99 per game. Our company is based in Europe and VAT/tax is included in the games' prices. This means that GOG.com will always charge you $5.99 or $9.99 per game. However please be advised that we are based in Europe and have no control over your bank's additional international/card transaction fees (where applicable).
I took that to mean they took care of any currency difference so that it would always be the advertised price - well now I know better - so basically gog is just like steam without the drm - now I get it, a bit irritating to work it out after though

SLIGHTLY ON-TOPIC DIVERSION: I'm temping in an office (an "until it's done" arrangement) and today everybody was jealously fawning over my ridiculous typing speed until I pointed out that I was totally shooting myself in the foot since I'm paid by the hour and I'm just making it so there aren't as many hours
OK work stories are boring, I won't do that again

They could word that better I guess as it must be a bit confusing for you guys with different dollars. Not sure about the steam reference as I thought they charged in local currency nowadays. I know we get charged in £s now.

Hmm, as naive as Blakes7's interpretation might sound (imagine how cheap the games would be in Japan!), he does have a point - the letters USD do not appear anywhere on the site, and that is kind of ridiculous. Definitely needs to be fixed.
I'm kind of surprised I never noticed this.

Uh, no. For Steam: 1US$ = 1 Euro (which piss off many continental European gamers). For GOG: 1US$ = whatever the exchange rate is, wherever you are.