When I got my x5, it only had one diamond key. Planning to keep the car for a while and wanting spares, multiple drivers, etc. I did the following, which may be a new solution you can consider:

1. I bought 3x valet keys (minor screw-up on that - I believed I was to be getting fully functional master keys [but no remote]; the only limitation in a valet key is locking the glove box) - ordered online for about $35 each from thebmwminipartstore.com. As with all genuine BMW keys, they came direct from BMW-USA, then went via thebmwminipartstore.com to me. They needed me to email a scan of my title and registration for obvious theft prevention reasons. This arrives pre-cut, and with the EWS pre-programmed, so they work, right out of the box, to manually unlock the driver's door lock and then start the car.

2. I bought 3x used genuine BMW diamond keys on eBay for about $15 each. I then cut the metal key part off, ground it smooth, and re-programmed the remaining diamond part to do the keyless entry, etc.

So now the cut-off diamond part is like a more traditional remote key fob. Full functionality that a diamond key would have, but in two parts. Net cost was around $50 each, for 3 sets = less than the cost of one diamond key at my local dealer, but this was all delivered to my door.

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2001 X5 3.0i, 203k miles, AT, owned since 2014