I use plugs when I only want a few of a certain variety. Some cabbages for example. I don't need 12 cabbages of each and buying seeds would leave a lot to throw away after a few years.
About 3 times each spring there is a market at the plots where we pay 15 ct for a plug. This year I was al little late sowing earlies and in the green house the mice ate all the pumpkins, cucumbers and and, so treated myself to some lettuce and cabbages to still have a few veg at the beginning of season
I am trying to get my own seeds as much as possible, but it hasn't worked out yet
Up till now just radish, brussel sprouts, celery, chervil, tomatoes, chillies, peppers and bear leek?..