I actually commented on how Steam had packaged all the Unreal games (which included an extra game - UT3) for a lesser price compared to the prices of all the Unreal games offered on GOG combined before somewhere on the GOG forums. Steam's offerings definitely was more attractive in that instance.
But that said, I've yet to purchase the Unreal package from Steam either, probably in hopes of GOG coming up with a matching packaged offering. I think purchasing games at GOG is at times more than just for the sake of monetary value or the lack of DRM.
Firstly, the quality of the releases we had from GOG (at least in those I have already bought) are great, many of which you can see the effort made by the GOG team to bring the game onto modern platforms.
Secondly, there is the great technical support provided by the GOG staff and the community. The community that GOG has built around these old games is definitely a plus point for me.
In terms of games as old as the ones offered at GOG, I would very much prefer making my purchase here even if it was slightly more expensive as I would am assured that the game would definitely work and even if not, I have a friendly group of GOG staff as well as the GOG community to seek technical help from.

the pricing is fine because the product is better.
fully patched, inc expansions, no DRM, nuff said.

Perhaps I'm just bitter from being burned, but my laptop absolutely cannot run Second Sight, it's not any one's fault really, my laptop was built without a specific kind of video card, which Second Sight requires. It plays on my desktop, just not on my laptop. It's just plain weird to me. I can run some orange box games (which I know my onboard video card doesn't support), and play other games like UT2k4 just fine.
Anyway, my point is, is there are some instances where there is NOTHING you can do to get it running. So be wary.

One thing where people tend to forget is that online delivery is not free and often uses distribution rights which incurrs costs, web designers which incurrs costs, delivery software and download managin and accounts software which means even more costs then there's the costs of the servers and the inevitable costs of tech support as a contracted part of the setup.
That's why internet delivery isn't as cheap as people think it should be.
Think about it rationally and the online sales of games will, in the future, come close or even rival shop sales. Why fight to find a parking space, which costs money, after a ten mile dash to the shops through traffic jams, blocked roads, avoiding suicidal buses when you can buy at home and download whilst watching the grass grow?
It may not be cheaper but it makes a heck of a lot more sense.

That said, no amount of tech support or forum advice can help simply because the game was not intended to run on that machine setup. It's like going online to ask about why I cannot get Metal Gear Solid 4 to run on my PC.
What I meant to say with my original statement however was that should I not be able to run the game, despite the fact that my system fulfills the system requirements, I can expect prompt aid from GOG and/or the GOG community.
Making sure the user's system fulfills the requirements, however, is solely the job of the user.

Please remove -- duplicate post.

One also has to think about the fact that physical copies of games that old have probably been sitting around for a while - long enough that the retailer just wants to push them out the door.
EDIT:\
In retrospect, I probably should've read beyond the first post before replying...

Since Steam uses DRM, and most physical cd/dvd installs do as well; it's comparing apples to oranges against GOG.com. GOG.com is DRM free, the only fair comparison is to any service that is completely DRM free and offers unlimited re-downloads; it would also have to have an awesome community like this. :)