Can anyone recommend a vendor who can help with a one-time dedupe project? I have a client with over 10K dupes that need to be merged but they don't need an ongoing service (they've stopped further dupes from being created). The vendors I'm aware of only offer on-going services. Marketo's Easy Merge used to be a great option but they jacked up the price and also re-designed their service to be more of an ongoing thing. We don't have a preference for whether the tool operates in SFDC or Marketo - though it would probably work best if it were in SFDC.
IMPORTANT update to my original question: the client also has Netsuite integrated into SFDC (via boomi) and the dupes must first be merged in NetSuite - then in SFDC.
You can try ZaapIT. Its easy to use and can help in identifying duplicates within leads, leads and contacts in SFDC.