actually the 3603 stuff is for lab. but yeah, im wondering the same thing as you.
the R-1000 cant take as high a PSI becuase its softer (and thus probably has a tighter bending radius). but even if you did sell your stuff for 10 cents more (o wow lol), id still save money (since i only need like 6 feet of the stuff). maybe you could price match
also, you could get 3/32" thick R-3603 for $2.13 in 10-ft lengths. i wonder how it conpares to 1/8" thick silicone in terms of bend radius? (cuz i got myself a somewhat tight bend lol)