Super-Cheap Toner Cartridges

I base my choice of home laser printer primarily on cost per page. I am on my second Brother printer, for that reason. But the prices I am seeing for TN350 cartridges on Amazon are setting new records for low-cost toner. I actually bought a couple 2 weeks ago for $10/cartrdige, from JR I think. I installed one yesterday, and have probably printed 50 pages. So far, so good.