I had been using AOS, but went looking for a cheaper alternative. Went with WCS and have been disappointed.
Based on a sample size of only one, their blocks are poured vertically and they don't finish the top end. As a result the surface is very irregular and rough. Water tends to get into the texture and dissolve the block from the end, leaving a brittle lattice of alum that soon becomes unusable.
An attempt to contact customer service via email got no response.