A good locksmith can cut the keys and program them. I’ve bought 315mHz keys on-line, had them cut and programmed for about $50 each. Now I have a MB Star diagnostic machine so I can program them myself.
To deal with an “all keys lost” situation, a Star diagnostic machine is a must.
In my experience, taking a Smart to the dealer for keys will result in a request to verify ownership in multiple ways (title, proof of residence, utility bills, etc), then the keys will be sent from Germany. Not terribly efficient, but very security minded. Been there, done that (refused the $495+ estimate).