If you sell something that can be posted or collected, yes, and sooner than you think. The moment a customer can pay at eleven at night without messaging you, you have stopped losing the sales that happen when you are asleep, driving, or busy with somebody else.
The cost is a percentage per transaction, usually somewhere around three percent, plus a small setup. On a R400 order that is about R12. Compare that with the order you never got because the customer had to wait for a reply, send a proof of payment, and hope somebody checked the bank.
The one mistake that makes it not worth it is putting a checkout on a site that does not show stock or prices properly. People will not pay for something they are not sure you have. Get the catalogue right first, then switch payments on. The order emails do the rest.