"Swedish metallers OPETH have sold more than 19,000 copies of their new album, "Watershed", in the United States in its first week of release to land at position No. 23 on The Billboard 200 chart."
In Flames:
"A Sense of Purpose" (Koch) shifted 20,000 copies in the United States during its first week of release. Billboard position: #28. This is slightly less than the opening tally of "Come Clarity" (Ferret), which sold just under 24,000 copies in February 2006 to debut at position No. 58."
So, as you can see In Flames sell more copies in the US, they just faced tougher competition during that period and hence ended up on a lower chart position. BUT, I remember that I was really surprised to see this back in june. Thought the difference would be much much bigger. Go Opeth, go!