Buying groups already exsist - Numark and Cambrian Alliance being 2 examples that spring to mind. Cambrian is mainly a buying group (properly independant though); Numark adds branding, special offers, training and support but is now owned by Rowlands (IIRC).
Implications are (hopefully) lower prices, some stability in prices, not spending time searching searching searching for the best prices. Numark adds "own-branded" stuff (meds and shop stuff) and a whole brand identity for indies, if wanted.
Barriers might include joining/subscription fees (though hopefully savings would massively outweigh) and the committment to use that group as your major supplier which might mean missing stuff elsewhere (not a committment very closely followed in my experience.....).