The math is simple...it's $60.00 a year. 10lbs of lye currently sells for $66.62. Times 20% = 13.32. 60/13.32 = 4.5. You would need to purchase 50lbs of lye a year to get that $60.00 back.
It would be worth it for me. I easily go through 50 lbs of lye and I can get the 20% off buying via Amazon where I have Prime and free shipping. You get two free drying trays a year if you post a product to the directory, free masks, blah blah blah plus more discounts. Only one small thing...with the discount, their lye would be $5.33/lb. I found a local soap supplier and can get it for $2.50/lb. But I do like their trays and I do like their molds. The free trays alone would make it with joining the club.