Last year I was looking at a couple of hand held devices that compacted compost so tightly that you did not need seed trays or pots. The first machine made a block about the same size as an ice cube, and then you made another larger block that had an indentation in in that you could put the first block into. Then there was another machine that made a bigger block to put that block into before finally transplanting to a large pot.
I found a couple of people selling there on amazon in the US, but one company wanted over $300 for it and the other one was out of stock.
Looking at the amount of money that I am likely to spend on various sizes of seed pots and trays this year that $300 is looking like a good deal. Plastic pots seem to be made of incredibly thin plastic these days, and I rarely get more than a couple of uses out of each pot.