How accurate does a Regency have to be?

I write at least three new Regency romantic adventures every year – sometimes four – as well as two mainstream historical novels set in World War II. Obviously with any books set in living memory it essential to get all historical details absolutely right so I tend to spend far longer on background reading and detailed research with these books than I do for my Regency romances.
One author, a friend who also writes Regency, said to me when I mentioned that she had made a couple of minor historical mistakes that as her books sold for less than £1 it didn't really matter. A reader would hardly expect a writer to spend as much time on these details if the book was going to be sold for so little.
What do you think? Is she right? Do readers get what they pay for and don't expect the same standard of historical accuracy in a less expensive book?
I think that every book, sold for whatever price, should be as well written and as accurate as the writer can make it. Of course, no reader was alive in the Regency and therefore less likely to be as knowledgeable about the period. However, many readers are fans of Jane Austen and will have gleaned a lot of accurate history from reading these books and watching TV and film versions.
I don't do as much research when writing a Regency story because my background knowledge is so extensive after having written more than thirty books in this genre.
What I do is check when I'm not sure – for instance I wanted to know what songs might have been sung around the piano at Christmas time. Hark the Herald Angel was written in the 1700s, so I used that, but I had to check online first.
I know that my books are more historically accurate nowadays than they were when I first started writing and I'm proud of that. I'm not talking about major anachronisms such as talking about turning on the tap or catching a bus which I've never done, but small details like using the word fiance, which wasn't around until much later.

What about covers? Not whether the picture on the front has the correct hair colouring as the heroine or hero, but whether the setting and costume are correct. In the cover on the right the girl looks exactly like my heroine – however, she wouldn't have worn a white dress with such a low back. I had to settle for a slight inaccuracy as it's almost impossible to get perfection if you use photographs rather than artwork for your covers.
 The cover on the left was for one of my early Regency novellas for My Weekly Pocket Novel. Need I say anymore?
A Runaway Bride is a recent book with a lovely cover from Jane Dixon-Smith and I thought it historically correct until a friend pointed out there was a zip running up the back which neither Jane nor I had noticed. Would you have noticed if I hadn't pointed it out to you? The MW PN cover is horrendous and totally misleading, however despite the minor inaccuracies, I think both the other covers give the feel of a Regency romance.
I've been told by some readers that too much "history" in a Regency spoils the romance and that as long as the setting and dialogue are reasonably correct, they don't even notice the details. The plot and character is what is important.
Do you agree? How much historical detail is too much and drowns the reader in unnecessary information? I'm not talking about a huge info dump – that's never a good idea. I like to put in details that bring the period to life and use the correct words when possible. If I call a bag a reticule then I make sure it's obvious from the context what it is.
I would be interested to hear your views.
Fenella J Miller