I assume you're talking about a scanning electron microscope (SEM) and not a transmission electron microscope (TEM). While both are rather expensive to purchase and maintain, the latter is much more so.
A new SEM from a major manufacturer like Hitachi, JEOL, or Phillips might run you $150K to $250K depending on configuration. Analytical add-ons such as an EDS detector and back-scatter imaging will add at least another $100K. Then there's the service contract that can run around $20K a year. And these numbers are from when I was in the lab business about 10 years ago.
If you are looking for a used instrument, they can be had for much less. There are used lab equipment brokers out there and a Google search will likely turn them up. While at the last lab I worked at in the mid 1990s I purchased a mid 1980s model Hitachi 540 SEM with a field emmission cathode that was being surplused from a local semiconductor fabrication operation for $5000. It had been used for imaging only so had none of the analytical extras, and we had to know how to move, re-install and maintain the thing. And this is where the cost comes in. A used instrument may be relatively inexpensive, but if you don't have the expertise to maintain it yourself and an inside relationship with someone associated with the manufacturer to get you spare parts, keeping it running will get real expensive real quick.
If you want to talk with someone who has done this sort of thing, look up Bart Cannon. He's in the Seattle area. Tony Nickisher (Excaliber Minerals) also runs an SEM and can likely fill you in on what it takes to have one of these toys in your garage.
Best of luck,
Jesse
