You might be able to show a saving for a year or two (assuming, that is, that you can find and recruit a tech with the skills required) ... but then, a couple of years down the line, how can you be sure that the guy will want to stick around?

An ultrasound guy will most likely be already working with one of the servicing companies (and therefore probably quite well paid). Audiology is a specialized area; as is endoscopy to a certain extent. A guy with good experience of all that stuff is likely to be quite "marketable", I would have thought. How are you going to attract such a person?