Just because it was "10 seconds" doesn't mean they shouldn't be able to charge for the service they provided. It still took a person to man the u/s besides the use of the machine. The amount of time it took is in line for the reason why you needed it.
Also 16 pictures is a lot of pictures for an NT scan. The scan was not for pictures but to check the nuchal fold and the other factors hence the amount of time. If the insurance company got a 45 minute u/s bill to check for a heartbeat they would've denied it and you would pay the full cost of the u/s.
Finally, $130 seems actually cheap. I had over 56 u/s between two pregnancies, some twice a week. All medically necessary, it just means that I met my deductible earlier.