The repairability of cracked brass cups depends on how deep the cracks actually go. The problem is that brass is a much more difficult metal to spin when it is fairly thick than copper. Copper is relatively soft and doesn't work harden as much as brass. Consequently, brass needs to be annealed much more often than copper when it is being spun. (Copper also needs to be annealed, but probably not as often.)

Cracks show up fairly often in the brass Paul Fox candy dishes that Danny Dew produced. Annealing these brass cups might stop further damage. It may be possible to polish out the cracks.

The problem with asking Jim Riser to repair these is that, like many magicians, he does not like Jeff Busby. He may or may not be inclined to repair these cups.

You can always ask him.

I can't speak for him.

In this case, I would probably put them on the shelf and let them be.