CGC slabbing costs money, but it is virtually required with books worth over $1,000 if you hope to get anything close to top dollar.
Purple label of death has that name for a reason, but selling a restored book will have the same problems. You are not losing money by having it slabbed. PLODs have anywhere from 80% of the value of unrestored, to 10% of the value, depending on the book and the work done to it. ASM #1 included. If it's just a tear seal, no big deal. If it has pieces added, or is trimmed, it's a huge deal.