Hi Susannah
Many thanks for the query (and to Ian for pointing it out, as I don't come here as often as I should!)
I agree that in most instances authors should expect some renumeration for their work, and as an author myself I always tend to approach paying markets before submitting work to non-paying markets. However, having run Elastic Press for five years now I'm much more aware of the constraints on time and money that publishing involves and it's a fact that some worthwhile projects wouldn't exist at all if it wasn't for writers submitting their work for free.
With the single-author collections we publish, our authors are renumerated on a 50% of the profits basis - it doesn't always amount to much, but we're glad we can pay at least something. However, for the anthologies, splitting profits amongst 20+ people would almost be an insult in the amount we'd be able to pay, and therefore we hope that writers are happy to submit stories for the kudos of being published by us in itself. As you say, we've won the BFS best anthology award three years running now, and whilst that doesn't (believe it or not) equate into tremendous sales (or any additional sales!), it does add credence to our publishing house and hopefully draws attention to us from people who wouldn't otherwise have heard of us - this raises the profile of the writers that we publish. Mentioning the "Extended Play" anthology for example, even the musicians who took part (both in writing for the book and performing at the launch) did so for free, perhaps realising that any publicity at all is better than a few pounds as a thank you.
Perhaps I should mention that in the five years running Elastic Press - mostly in my spare time as an overgrown hobby - I've never drawn a penny out of the profits for myself, and all the money I make is ploughed back into the company to promote new authors who excite me. And we focus on new writers, mixed genre, short stories - the three things which most booksellers are very reluctant to stock! - so selling ANY books at all is always a struggle, never mind making a profit from it
If you look at ralan.com you'll see there are many magazines listed who only pay in copies, and that's because if they paid in cash there would only ever be one or two issues of that magazine. Small publishers - in the main - are lucky to cover their costs; often no more. And as I say, we do pay on our collections, although not the anthologies for reasons mentioned above.
There's more I could say (but my spaghetti is ready!). I'm interested in your response and any others who might want to add to the topic too!