In my 1998 528i, the compressor is made by DENSO.

If you can get DENSO, then it is a good brand.
- Evac ($30 at local shop)
- Replace the compressor, incl. all O-rings
- Vacuum + recharge ($70 at local shop)

So the cost will be:
- DENSO compressor, your labor
- Labor from local shop = $100.

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT