It is a cheap hobby. Try boating, skiing, cars, &c, &c.
I have only one, um, real fermenter (30L), but I have a couple of HDPE cubes at 25L each. They're a bit small for 23L fermentations, but they're okay usually for 18-19L batches. Quite often if I'm using a kit, I just make it up to 18L instead of 23L anyway. Alternatively, I can rack a 23L brew from the bigger fermenter to either one of the 25L cubes or an 18L brew to one of a couple of 20L cubes (picked up from the back of a cafe - nothing like a good scrounge).
Given that I don't have space for a brewing fridge and therefore cannot brew over the summer[*] I tend to have a couple of brews either in primary or secondary at any one time.
T.
[*]A week ago I discovered Saison. Man, my brewing world is about to change! It looks like people routinely ferment Saisons in the low to mid 20s which means I can probably brew Saison all summer! Yippee!