It can vary depending on what size the thing is. Klickys run about $2 to $2.50 I would expect a horse in the $1.75 to $2.50 range. At this point they probably only have newer style horses. If there are any old style left they will be the common plain colors white, black, etc.
Small pieces like cuffs run about .15 to 25
Since you aren't sure about pricing or what they will have I would recommend you make three lists. One of the things you have to have, one of the things you want, and one of the things you sort of want. Then when you place the order start with the most wanted list, get a subtotal when you come to the end of it and then judge from there how much farther to go.