should be able to get them for you for that ($6.00), that is about the going rate, and shipping will kill you on one starfish. If the star is healthy it will probably last the shrimp about month, so buying more than one would require another tank. Choclate chip stars are not
reef safe, and the star will be alive and feeding on your reef while the shrimp is riding around feeding on the star IMO
, harlequins prefer a star more like the linckia, the softer skin and that body style. I have heard of people using harlequins to reduce the number of small stars similar to this one..
You might could find several of these on some LR
and add them to your tank, they will naturally reproduce and add a continual food source for your shrimp, and if the small star goes south quick, there is less chance of fouling the tank. Not real sure if it's feasable, but it is just a thought.