Kellvin, if you are convinced that all groups are out to "rip you off" then you are probably best not joining one. Aircraft ownership, whether singly or in shares, is never a fixed-price experience. There is always that unexpected maintanance bill or component failure - which is always, at least, a treble-digit bill (have you heard the one about the Arrow with the £33,000 annual?). In a group you have people to share that pain and expense; which is part of the reason why the total of shares is generally a little more than buying a whole aircraft.
If you are stretching your finances too far to allow for any surprises then you need to look in another direction. Maybe the PFA? At least you won't be "ripped off" by engineers.........