$45 dollars is a very good price for a set of strut extenders. I bought two sets from Boondox back in about November of last year. As I have stated in earlier threads, they wouldn't screw down over the shoulder of the struts and i used an air dremmel to gain the needed clearance on the strut shafts so they would fit.
On my second set, I took them over to my neighbor's tool shop along with another new Monroe strut. He mic'd the shaft thickness at .666, then he mic'd the internal width of the strut extender and found it was .002 under the strut clearance required. He placed both of my strut extenders in his lathe and cut away the needed clearance. He noted the inside of the strut extenders were out of round (= he didn't have to take metal off of all the inside... just "high points"). By the way, they were made of standard "soft" steel. he cleanranced my strut exteneders for free, bless his heart.
Now the strut extenders screw onto the struts very cleanly and snugly. In fact, the oil I placed on the shaft caused a vapor lock when i tried to unscrew them.
I asked him how much it would cost to fab a set of these. He estimated (in his head, he didn't run a calculator on the costs) that fabbing a pair of these would run about $300 or $150 each. That's making them out of a little stiffer quality steel also.
He estimated to bring the costs down on these to around $50 a pair he would have to work an order in the area of about 100 pair of extenders. He's a small shop, but he's been "in the business" for about 20 years and I take his knowledge and experience as pretty accurate.
So apparently these extenders are being jobbed out to chinese manufactures (my guess) which explains the quality (or lack there of) and also the difficulty in obtaining them when your on hand stock runs out as apparently has happened to several dealers.
Norm