Can an accepted offer be a lowball offer too?

Why would I return an item if the SELLER has regrets?

Because evidently you have regrets too, as the buyer.

I made an offer on something, paid promptly, and received the item which as not in the excellent condition as advertised. I mentioned that and then the "lowball" word came out.

It seems that the seller was not happy with the price, and the buyer was not happy with the stated condition.

Were you trying to renegotiate the sale price after the fact due to your regrets about the condition?

Recently, about two months ago, I was asked to take something back, and I refused. The buyer told me that an amp I shipped him arrived in excellent condition, as advertised. Then, a few days later, he told me that it did not work as well with his speakers as he hoped it would, and asked me if he could return it to me for a refund. I told him that I was not an audio store, and that I do not accept returns due to system synergy issues.
Sheesh, some buyers these days expect it all. They want used prices, but new price services.

Part of this internet trading thing also depends on quality buyers.  Yes, there are some rude and shady sellers. However, there are also some rude and shady buyers. The water is full of sharks, sellers and buyers beware.