Yeah, I'd say jump on it. It is a very good deal. With SL8s being officially discontinued, you're unlikely to see that price too often.
The older roller-locked HKs are must haves for collectors. I want to get into a full set, over time myself. Price for these guns seems to pretty much have settled right into the $3000 range, depending on condition. But I don't know that I'd shoot real HKs that much. Maybe a trip to the range now and again.. but if they were NIB unfired, I'd be taking a serious loss. And if they are in good to excellent conditions, putting a hammering on them wouldn't help their value either. Thats a lot of money for a set of black safe queens.
With the SL8 at that price, you have some nice wiggle room to convert it or set it up how you like, and then you can shoot the snot out of it.