Deductions & credits

Yes, some thrift store items go for more than others.
So while it might be common for most boots and shoes to go for $5 a pair in your area thrift store, other premium brands or newer pairs might go for higher.  Just be reasonable.   
Your donation is worth what's called the fair market value.  This value is the amount someone would willingly pay for the item.  You can estimate it by determining what you'd pay for the item at a thrift store.
@savesomemoney