I notice that Desktop Metal doesn't show their oven in the video. That's the big, expensive, somewhat hazardous unit. "Easily swappable aluminum gas canisters ... safe to use on the shop floor" says the data sheet.[2]
Wazer, the low-end water jet cutter that's still stuck at "pre-order", has a similar problem. They're trying to make a somewhat messy industrial process less messy. There's some hand-waving involved. You end up with a sludge that's a mixture of water, shattered garnet, and whatever you're cutting. They gloss over what you have to do to dispose of that.
[1] https://www.youtube.com/watch?v=B9VOwqtOglg [2] https://desktopmetal.s3.amazonaws.com/Studio-office_friendly...
https://www.youtube.com/watch?v=a-FHY5FNsWc
12 minutes uncut. They go from printed model to working cast piece.
All new, Kaya Cast vac chamber they use is $1k, the Paragon kiln is $800, and the Electro-melt furnace is $350. Add in safety gear and incidentals and you are looking at 3-4 thousand dollars to go from a 3d print to a cast metal piece. Heck, depending on the complexity, the vac may be optional.
(The "maker movement" may have run its course. TechShop seems to be in financial trouble.[1])
Casting aluminum is easy, but not very useful. Doing this yourself you can't guarantee grain structure/size, inclusions/porosity, or temper. Plus it's usually plenty easy to mill from billet since aluminum is so soft.
Gold/silver is also relatively easy. You need better equipment since the temperatures are 2x higher. Strength isn't important, so casting stuff in gold/silver is quite common. Outside of jewelry there is basically no need for it.
Casting something more complex like good steels, or platinum, or nickel alloys- casting will be very difficult. Molds aren't so trivial, you need preheats, and a mistake leads to liquid metal on the floor or an explosion.
Sintering can be used with challenging alloys and requires almost no expertise. Everything comes certified and gets heat treated in the oven. If your time is valuable enough to warrant a metal 3d printer, it's valuable enough to make learning an entire discipline too expensive.