Soholm does seem to do poorly on eBay, but it does surprisingly well at antique fairs and in specialist mid-century design shops. I was at a fair yesterday, and a Noomi Backhausen floorvase with some damage sold quite quickly for just under ?100, and I know someone who regularly sells the large wall-plaques to a mid-century dealer in Nottingham for between ?90 -120 each - and they in turn must be selling them again for at least twice that.
I have one large and really abstract Soholm wall plaque by Noomi Backhausen that I really like. It's a really amazing piece with a thick glaze composed of coloured glass chips arranged in the various recesses and then fused. I'll try to get around to photographing it.