No. All fees are clearly displayed before you confirm any transaction, and there is no penalty for selling at any time.
The costs you should expect are the ones in the published schedule: the premium or discount to the spot price, included in the buy and sell prices and shown before you confirm; a 1.00% commission plus 5% VAT (1.05% in total) on each purchase and each sale, and the annual storage fee (0.50% gold, 1.00% silver, plus 5% VAT).
We charge only the fees published on our Fees and Spread page. Your own bank may charge fees for transfers; those are set by your bank, not by Eona.