Is this a fair deal for Coots Mix (135 gallons) for a 4x4 soil bed. Idk if $700 is overpriced.

That’s a bit pricey

For build your own that seems pricey, does that include shipping?

I would really try to find the things you need locally, even if you have to drive for a bit. The only time I'd order that much soil from BAS is if money were really no object for me-which, if this is the situation you are in then go for it! If you want to try to save money, you will save a lot if you can find any part of the mix locally, especially the "aeration", which is so expensive to ship. Lots of times you can find local compost/ewc/peat too. The last time I mixed up some Coots mix, the only thing I couldn't find nearby was the pumice/lava rock, so I just used Perlite and saved like $400. I'm also really liking rice hulls for aeration these days and with those, you just need to add more when they break down. I would like to see arsenic #s on them though.