Growing medium

I am having a difficult time finding vermiculite at a reasonable price.
Could I use potting soil mixed with peat and compost?
Or, could I use it by itself?

two things, imo.

- cut back on what you put in. last year, i put in a bag or two less than was called for and still had a great season in the garden. you could work it back to the correct level over time by adding next year, and the next... this is a one time investment, imo. you set it up right, and you are done. peat moss and vermiculite dont decompose. you shouldn't have to change/add any going forward....just compost. do it right, but do it affordably would be my recommendation.

- try some alternative sources. pearlite seems to be the most common alternate. the theory behind the vermiculite and pearlite substances, if i understand correctly, is that you need water retention to make your garden more efficient. if you have a substance that holds water, you water less and save money and time. that's the whole idea behind sfg....saving money, space, and time. vermiculite, apparently, expands and contracts as it heats up and cools down. this keeps aerating your soil, too....and added benefit to keeping things loose and workable.

hope you get some more help on the alternative substances part. i have been lucky enough to find vermiculite in my area.

Check with your local nursery or florist. They may not stock it, but ask if they can order bulk vermiculite