If a small merchant sent you $60 more of product than you paid for, would you send them money for it?

I ordered and paid for a smaller size and received a bigger size (along with a paper receipt for the smaller size, so this was a packing error).

This is a superb, well-priced product that I plan to order from them again.

Legally I think it’s mine to keep but I don’t care about that, I’m asking an ethical question.

I really like this small business and although it’s been going for decades, it’s pretty specialized and I think run by just a few people. And nobody I’ve found sells a better version of this product.

I like to be careful with money but I can afford the $60 and I would’ve spent it on more of this product in the future.

(In practice it would be easy; I paid with zelle [which is like paypal, you choose any amount to send to an email address] so I could just send another payment.)