Get quotes, hangers, lab dips and a bulk sample
Test at a laboratory, against the tests the spec names.
A fabric quote comes with its validity date, a hanger of the actual cloth, lab dips for each shade and, before bulk, a bulk sample tested at a laboratory for weight, width, shrinkage and colour fastness against the grades in the spec. Judge each against the spec from step 1, not against each other: three quotes for three slightly different constructions is the oldest trick in the trade. Ask whether the hanger came off the same construction and finish route the price assumes, because if it did not, the hanger is not the cloth you will get.
What a bad answer looks like: a hanger with no construction written on it, or “lab dips after order confirmation” when the shade band is the thing the order will be judged on.