I use a peat based commercial grow mix in my greenhouse tomato buckets that contains mycorrhizal fungi - it costs the same and is a cheep additive...

I once took part in a lab test on them which proved to be ineffective, but that was only one small test. I think though that they could be a bit like the yogurts, which are sold with active bacteria, they may help if your gut flora is damaged or lacking those species, but otherwise they are just a waste of money, and as it is unlikely your gut is deficient, they are nearly always a waste of money.

Most of the recent scientific literature is only tested on cotton and soybeans, In mono cultures. Most of the studies are conflicting and show positive results only under very specific conditions, there were also multiple studies with negative results, as well as cautions about knowing the potentcy of off the shelf manufactured spores. They are very heat sensitive and can go sterile from being in a hot truck or warehouse. Best of luck.

Unless you are planting in sterile soil or bare soil, it is probably a waste of money . Your soil already contains copious amounts of these fungi, the ones that are there are native to YOUR soil and will benefit plants that are acclimated to your area. If you are planting in containers or using large amounts of potting soil, then they may be a decent additive. You would be able to get the same inoculation by mixing in native soil.