Unless they are touring that is the amount the band gets per month. This summer the band made much more than 1000 pounds a month for each band member, but they need to plan for the months in the next few years when they dont have a brand new album out. The money they made in August needs to be saved so that they can steal eat a year from now, or two years from now. Also, they have overhead. They need to store their instruments, they need to pay their employees. When touring there is a whole crew to support, equipment to rent and travel to book. A lot of the money they get goes right back into keeping the band going. I dont think the 1000 pounds a month thing is too far off. He makes about 2 grand a month, plus bonuses if the year went well and if there was touring this will be supplemented. This year there was probably a signing bonus from Roadrunner and of course touring money from ticket sales and merchandise. All in all its not that glamourous and people shoud probably listen to this interview before posting about how Opeth is gay now because their shirts are for sale at Hot Topic (which they're not anyway.)
Very few people will ever work so hard to give you something so beautiful and ask for so little in return.