The first thing you need to know is that all groups are certainly not the same, it's as important to know what's not on offer - as it is to know what is!
You may not be getting the rebate you're due - A group that pays you a higher discount than you get currently is obviously a good thing. However, if they can't actually calculate what that value is for you and furthermore make sure that you get it; then you may find that you're not getting all that you're due.
You may not be paying the cost price you think - A group that can tell you what your cost price is through them is obviously a good thing. However, if they then don't make sure that you get that discount and on the value of your own practices purchases, then you might be paying more than you think.
You may not be treated equally to your fellow members - A group that offers additional discount benefits to its members, by definition, is beneficial for the majority of practices. However, those benefits may well not be apportioned equally and therefore you may not be treated as equally as your fellow members.
You may not be getting the best offer from your manufacturer representative - A group that works with suppliers to create transparency in costs to clients is a good thing. However, those that will not tell the manufacturer what products of theirs are being sold where, and at what price; have to be treated with a great deal of scepticism.
Your rebate payment may not be verified - A group that does no validation of any kind and only hands out monies as given to it by manufacturers, is coaching the profession to unconditionally accept the monies paid to them as being accurate. In my opinion that is a very dangerous precedent to set.
You may not be able to check your nett prices - A group that does not allow its members the ability to easily check the prices that they have been quoted, or those that they pay, are letting them down. Moreover, one has to question a group's motives for not doing so.
Vetcel shows, online, the nett/nett cost price of all products post discounts for its members 24/7 and then we make sure that they get them. The manufacturers can also see their products prices so are aware of what we charge practices.