how is spending stamina equate to being free is any way shape or form?

Free means no cost of any kind.

With as much as it costs to upgrade to level 7 guild, combined with the massive cool down, combined with the fact this buff should be better then the previous buffs, if this lab chance costs stamina,gems, or both its a rip off. If it does cost gems and/or stamina it should be a level 3 buff not a level 7.