Pac-Man and Galaga have been sold out on GS for a long time, though Pac-Man can still be found at other retailers linked to on the Numskull site. Very disappointing that there wasn't a sale on these, but this has been THE year for lovers of disappointment. Replicade must produce far fewer units, as their cabs (with the exception of DL, for now) are long gone, save Ebay and Amazon marketplace sellers with ridiculous markups.
Yeah, the Replicades SF & Tempest just sold out in the last month or so, as I got emails from NWT stating stock was limited, and buy now, or not at all. Centipede went awhile back, but that was first and had good reviews, but it lasted ages as well. The Replicades were also all spread out over time, and more likely to be bought due to there lower cost.
The Quarter Arcade Ms Pac, Galaxian and Galaga all got released within 1-2 months of one another(last year), which meant not everyone could buy them at the same time($150-$200). If not for the $100 I got them for, I wouldn't have gotten what I did, and that's why I'm still waiting on Galaxian. The only Galaxian deal I've heard of was from Walmart, and while they used to carry them all, it seems Pac-Man is all that's left. These also take up way more space than the Replicade, so most retailers probably don't want a niche item like this taking up space, due to slower sells.
But if I had to guess, I would say both are dealing in similar numbers, but Replicade is cheaper, and for something like DL, offers just as much detail at a lower price than QA(shipping is much cheaper as well). Both are well worth their prospective asking price, but both are a hard sell to anyone who isn't a diehard 80's arcade kid. As you can get bigger more full size A1Up for less in many cases, and that seems more inviting to most, especially for those who don't care for arcade accuracy.