I guess it depends what kind of accelerator we're talking about. The '030 cards are fairly common, and sell for ~$200 generally. AmigaKit has had some listed at $229 for months now, either they've got a ton of them or people are holding out for something better, or are finding what they need on the used market. I doubt a newly designed and manufactured card could compete with those prices.
The '040s and (especially) '060s are another story as there seem to be a lot less of them kicking around.
As for simple RAM cards, I've never paid much attention to those when it comes to the 1200, but from what I've seen they do sell for a bit more than I'd pay for one.