You can have the camber adjusted, it's pretty easy, shouldn't cost an arm and a leg...realistically it's one bolt for each wheel??? It's a nut, bolt and "cam" style washer on the early E36's, not sure about the later models though. I fiddled about with it on my car and i had the wheel pointing massively inwards just for a laugh, but then had all the alignment done properly including the camber so i'll leave it alone until something goes wrong...
Are you certain the tyres are wearing unevenly because of this camber? It may be under-inflated/over-inflated rear tyres. Could be worth having th e alignment checked, as your rear wheels may be pointing outwards (toe out), and therefore would "scrub" the inside of the tyres, and consequently they would wear out faster. I also had this before but mine were pointing inwards and wore out the outside of the tyre?
Get the alignment checked out, or do it yourself...
You'll probably get some tips from others, but a simple rule of aligning the rear wheels is to point them towards the front wheels! Not simple to explain, but use a long bit of wood, and you have to hold it flush against the rim of one of the rear wheels, whilst looking along the inside edge of the wood (the edge touching the rim) you should be able to tell if the wheel is pointing inwards, outwards, or there or there abouts...
Now this is only a quick check to do, but you could just pay £40 or so and have it done by your friendly wheel alignment chap!
Hope this helps
Edited by Blackcat