I had sticker shock when I went looking for them too.
My solution is:
Plastic and fiber egg trays with little holes punched in the bottom for seed starting and a biggish table spoon filed/ground down to work as a tiny shovel. The little 'shovel' worked well for scooping out little strawberry plants.
Transfer to small, generic "solo" cups with holes melted into the bottom with a soldering iron.
Working on collecting 1 and 2 liter bottles for SIPs. Have built a jig out of scrap lumber and 1/2" plywood to make marking and cutting them easier, so I end up with SIPs that are pretty much identical.
I'm kind of stuck on what to use for trays to put the egg cartons and solo cups in though. Did take a bunch of scrap 2x lumber and ripped it down to "1x2" and built some old style, divided, milk crates to hold nine 2 liter SIPs.
(Will own up to having an obstinate streak which will not allow me to buy something I feel like I am paying too much for - doesn't matter what the actual cost is.)
I don't believe we can resist the things which make no sense - I believe.