The answer is yes. You do not need to be subscribed to be able to purchase items or sets on Iconfinder. Instead, you can use the Pay-as-you-go option (to buy items on demand without being tied to a subscription). To start buying, you first need to make a prepayment to your Iconfinder account balance. For this, follow the steps in this article: How to make a prepayment to your account. Once your account balance is positive, you can already start buying icons or illustrations.
Please note that in order to add money to your account, you must be a registered Iconfinder user.
Read more about the Pay-as-you-go option.