check ebay and see if you can find those items and check out their prices because those are more accurate to what the buyer will pay, but here is what the beckett (august issue) says:
Metagross ex(there are two): Power Keepers: $6-12; Hidden Legends $5-10
Latias ex: $10-18
Muk ex: $4-8
Magmar ex: $2-5
Chansey ex: $2-5
Blissey ex: $8-16
Golem ex: $10-20
Hope this helps, of course condition is important but if they are in Mint/NM like you said then your'e all set!