No.

If you export your seed and import it into a decent wallet, the decent wallet will be able to spend the funds of your blockchain wallet directly. No extra fee for importing your seed...
You'll need to pay a tx fee when you create a transaction tough, this is independant of the wallet you use, but the process of exporting your seed from blockchain and importing it into a decent wallet is purely technical, it only costs your time.



By the way: exporting your seed from blockchain and importing it into a decent wallet decreases your security. You now have an online wallet that's saved on blockchain's servers (encrypted, but still), you potentially have the seed on other media, and you have a desktop wallet using the same seed... It's a good idear to empty this wallet completely by creating a new desktop wallet in a safe way and moving all your funds from your blockchain wallet to your decent wallet as soon as it's convenient to you.

All this being said, don't hold 7+BTC in a blockchain wallet... Really... A trezor costs ~0.008 BTC and is a lot safer than any online wallet.
A decent desktop wallet is safer than your blockchain wallet, but defenately not as safe as a hardware wallet.