Benchmark: timing 5000000 iterations of MakeThousands, Thousandformat...
MakeThousands: -1 wallclock secs ( 0.06 usr +  0.00 sys =  0.06 CPU) @ 83333333.33/s (n=5000000)
Thousandformat:  1 wallclock secs ( 0.12 usr +  0.00 sys =  0.12 CPU) @ 41666666.67/s (n=5000000)