Realistically speaking, slabbed coins are worth no more than raw coins. All slabbing does is help take most of the guesswork out of the grading. A raw MS63 1916 standing liberty quarter is worth the same as a MS63 1916 standing liberty quarter in a PCGS slab. The seller on the raw one might say it is a MS64 while the buyer might say it is a MS62, but with the slab it has been reviewed by professionals. Bottom line is slabbing does NOT increase the value, it only assists with determining the grade.