Those kits are nice, but I just use Dixie cups with a few hole poked in the bottom, and potting mix or a combo of seed starter and potting mix-I used the kit the first year though.
Then I use stuff from the deli, like cakes come in. Put the Dixie cups on the base, cover with the clear plastic dome, and put a couple of toothpicks under the dome, so that a little air can get in, but keeps it from drying out.
The Dixie cups and repurposed containers with potting mix or seed starter is cheaper than the kits, and works just as well.
I’m looking at a stack of mostly small Styrofoam cups I’m collecting for exactly that......basically free and easy to break apart.
Ran across this the other day. There is a plastic bottle hack where you can make a self-watering seed starter! It is at about 8:25. So clever!