The radius doesn't have to be large; my eggbeaters have about a 1.5mm radius around the shafts and have been fine so far. I also have spacers on the shafts and I just added a simple chamfer inside the spacer to clear the shaft radius - it only added a few minutes to make each spacer.

Cutting the radii around the teeth can be partly done in the waterjetting stage and the pockets for the inserts can be machined out with a rounded edge end mill. I have used a 1/2" diameter cobalt steel cutter with a 0.06" edge radius to pocket S7 steel and the parts have not stress cracked in 6 years. Rounded edge end mills are very durable and outlast regular end mills by many times. My 1/2" end mills cost $34 and are probably the most used cutters I have.