V.B.
No, they don't have sales per se. The price is the price is the price. Unless you shop during tax free season (back to school, and qualify for those parameters), you will pay the going rate like everyone else. I know the discount isn't a lot (typically 10-15%) on a refurb, but that's all I buy in the way of major Mac equipment. We are on our 2nd iMac refurb. Our first iMac lasted around 5 years, then the 2nd (our first refurb) lasted I think about 6 (?) and I am currently using our 3rd (2nd refurb).
I have actually been told that refurb is even a better deal, b/c not only do they come with the exact same warranty as a brand new out of the box one, it has been gone over AGAIN with a fine toothed comb by the refurb people at Apple. So you have even less chance of having a problem with it than one never returned to the company after purchase. I don't know that that's true, but I certainly have no complaints with either of ours. Once taken out of the box, you cannot tell that it is not brand new in any way whatsoever. In fact, you can't tell from just looking at the box, either. It comes with all the same stuff and brand new packaging.
That's about the only *bargain* you're likely to find. Good luck.
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ETA: oh and yes, if it is full memory that is slowing it down (google how to see how much you have available if you don't know how to do it), you might be able to add it. It depends on your particular machine and how it's configured and what's inside. I added memory to my last refurb iMac for about $40 and it extended the life of it for another year by adding space to upgrade OS systems.