This is an interesting question. One that I think is worth revisiting. It is easy to forget that the pancreas is attached to liver, which absorbs about half of its release. (not sure to what effect). Not to mention, the non-D stomach empties slower, and as mentioned, human insulin is extremely potent. The amount of insulin in their blood must be negligible.
Jen had the right book (Type 1 Diabetes by Hanas) but mis-remembered the figures. According to the book (and cited to the science papers if you want to look them up) a non-insulin-resistant non-diabetic produces about .5 unit of insulin per killogram of body weight (or .23 unit/lb).
The amount of insulin a non-insulin-resistant type 1 diabetic requires depends on time since diagnosis and age. And it also certainly does depend on weight, just as that of a non-diabetic does. According to the book the average for an early onset T1 by the time they are adults is .7 to .8 units per kilogram. But of course this amount will tend to be less if someone is a LADA or in honeymoon or getting lots of exercise or eating a very low carb diet or experiencing poor control with lots of highs. Just as it will tend to be higher in someone who has insulin resistance or little exercise or eating a very high carb diet. And as always, YDMV (your diabetes may vary), but this is a good starting point.