Sorry, is Sewn by not rarer than double exceptional? I have about 50 suits of double exceptional armor/items with shields and weapons, but only about 7 Sewn by items. And this is double blessed. Normal double blessed items go for 10m to 50m all day long. Those are normal, nothing special exception being (blessed), blessed.
I have only even saw a Sewn by, double blessed item 4 or 5 times. I have about 5 double blessed, double exceptional items, which the market for are 85m-150m all day, depending on the item. At the last Rares fest for instance, a double blessed, double exceptional wizard's hat went for 120-150m or so, I don't remember because I quit bidding then.
This one isn't a double blessed / double exceptional wizard's hat for sure, but is worth at least 100m I would think... The body sash is worth a little less than a wizard's hat or tunic though, perhaps. If you wanted to sell it, I would sell it on vendor search though. Just aim a little high of where you think and lower the price every few days until someone wants it enough. Those things do sell at some price, I can promise you. I would aim higher than lower though, because that one seems rare to me. I don't have one... and that's saying something. Best of luck for sure, peace all.