You did not mention if the closing fee was imposed because you chose to close the account before the contract expiration date. If you did close the account before the term was up, a fee is not uncommon in the industry and as you wrote, it was disclosed to you. Pricing is based on volume, average transaction and mode of processing. All Processors are billed the exact same Interchange and Association fees from the the Card Associations and these exact fees are passed through to the merchant at every single merchant processor. Each company will have their own processing costs to maintain through fees to the merchant so it's a business decision as to who you think is presenting the cheapest pricing. However, the lowest processing cost quoted may not necessarily be the most cost effective company to contract with.
Real costs are involved in opening and maintaining accounts often times thousands of dollars a year. Most processors will amorize these costs over the term of a contract. If you close your account early, the processor is left underwater on your account and will charge you a penalty for breaking the term of your contract.
The reason Elavon probably said it would take at least 30 days to close your account (of which you would continue to pay) is because merchant accounts are not just shut off. Your customers must be able to return goods or services and present chargebacks for a mandated period of time. Elavon must continue to keep your account open to address these transactions. Depending on your business and if delayed delivery is a factor, this process can take months.
Every fee you will be charged is disclosed on your contract. A business owner must take responsibility for comprehending the entire contract, not just what they think their rate is going to be. Good luck.