Three mana is a tad on the expensive side given that you also need to pay the cost of the spell you flashback, but its still doable
they're perfect for building decks, playing Limited games with friends, and are tons of fun to open #9
Golgari can brick off the opponent's offense and play enough removal to keep the battlefield empty, but also close the door when needed, unlike Rakdos, where you lose access to giant green creatures
If youre good at stocking your graveyard, you might want the newer, cheaper option instead
That being said, while these groups do have tight control of the market, basic market principles will still apply
Then at the beginning of your combat make a free 2/2 all colors Elemental if you control at least five Towns, and then your eight-mana all colors activated ability can pump your team by your Town size