First, HBC never "made" blankets, they just sold them. Other companies made the blankets for them, and put the HBC label on them.
Second, Witney was just one of several companies over the years that made blankets for HBC. But they also sold their blankets themselves under their own label.
So an HBC blanket made say it is made by Witney, and a Witney blanket may say that it is made for HBC. The "quality" should be similar.
The Witney company went out of business around 1 1/2 to 2 years ago. New blankets by them are still out there, but no new ones from the factory/company itself.
New Witney/HBC blankets generally run between $125 and $300 or MORE, depending upon size! You can expect to pay around $175 for a new 3-point from a retailer, if you search around for a deal.
So $90 might and might not be a good deal on that particular blanket. It all depends upon the size/color/condition.
Yes, there are cheaper deals out there if you look around. Most of those "cheaper deals" are military surplus blankets. The sizes tend to be smaller (narrow-er for use with army bunks), and the colors and patterns seldom match documented orginal trade blankets --- or most any documented early blankets.
The white candi-stripe or multi-stripe blanket tends to be the most common HBC style blanket you can find available out there. But the earliest documented reference to that color pattern that has so far been found is 1795. It generally came into use in 1810 to 1830 - the western Rocky Mountain Fur Trade era and after.
Those "pastel" colors, or "earth tone" colors only came into use in the early 1900's. So any blanket with a stripe at each end that is not indigo/dark blue, black, or full red, is probably from the 1900's. Common examples of these are light blue blanket with darker blue stripe, tan with brown stripe, red/pink with maroon stripe, pale green with dark green stripe.
So a lot depends upon the size of your blanket, and the actual colors and stripe patterns. And if you go over to evil-bay and search for "HBC blanket", "witney blanket", "point blanket", or "trade blanket", you will see lots of current ones being offered. And you can get some idea of what those modern antique collectors are paying for blankets.
Of course, these are but my humble opinions, and best used in conjunction with your own research.
Mikey - that grumpy ol' German blacksmith out in the Hinterlands
p.s. A friend researched and cataloged the listings of blankets on many many trade goods lists from up around the Great Lakes fur trade areas. Most "trade" blankets were manufactured and sold as doubles - two blankets woven as one long blanket. When a single blanket was sold/traded, the pair was cut/torn into two separate ones. The most common color combo he found was white with dark indigo stripes at each end, and red with indigo stripes coming in second. The most common size was 2 1/2 points. But he also pointed out that most of us had a 4 to 6 point arse to cover!