1. The power requirements to run one of these would be larger than what would fit in a basic Cubesat form factor. It's not going to be a 1U, perhaps something like a 3U or 6U at best. Then there is the thermal management of the large power supply (getting rid of heat in a vacuum is not simple) which is even more equipment and mass. Those larger satellites are a bit more expensive.
2. A lot of the "Launch a 1U Cubesat for $100k" figures are for the launch itself. That ignores other stuff like engineer wages, legal, etc. and is mostly hyperbole. Launching two for $200k is much more common as the second one take a lot less time to put together once the initial R&D is done. Then these "$100k" Cubesats, capability wise, are fairly useless. Think Sputnik type satellites. Want a working payload? Prepare to do more R&D. Oh and Cubesats have about a 50% rate of actually operating in orbit. First one doesn't work? Now you need to find more money to launch another if you weren't lucky.
3. The number of people who are willing to throw millions after something that currently isn't explained by science and is a lot harder to debug when you don't have someone sitting next to it in orbit, when it can done on the ground for an order of magnitude cheaper, is very small. Most people interested in using this are waiting for someone to pay for the testing first. Hell most satellite engineers I know for now still believe it to either be a hoax or will end up being just a measurement error. So people are riding this out until there is more hard evidence.
Milner is a billionaire. He could easily pay for a full-size satellite lofted up by one of Musk's $5M reusable Falcon 9 boosters in a couple of years... Double that number to build the satellite if you have to and he could still find the change in his pockets...
EDIT: and once I convince Milner to finance this boondoggle can I sign you up to be my lead satellite engineer?
2. A lot of the "Launch a 1U Cubesat for $100k" figures are for the launch itself. That ignores other stuff like engineer wages, legal, etc. and is mostly hyperbole. Launching two for $200k is much more common as the second one take a lot less time to put together once the initial R&D is done. Then these "$100k" Cubesats, capability wise, are fairly useless. Think Sputnik type satellites. Want a working payload? Prepare to do more R&D. Oh and Cubesats have about a 50% rate of actually operating in orbit. First one doesn't work? Now you need to find more money to launch another if you weren't lucky.
3. The number of people who are willing to throw millions after something that currently isn't explained by science and is a lot harder to debug when you don't have someone sitting next to it in orbit, when it can done on the ground for an order of magnitude cheaper, is very small. Most people interested in using this are waiting for someone to pay for the testing first. Hell most satellite engineers I know for now still believe it to either be a hoax or will end up being just a measurement error. So people are riding this out until there is more hard evidence.
Disclaimer: I'm a Cubesat engineer