I know there are cheap DDS chips, but they require filters and control logic. This one goes from 100 KHz to 20MHz with just a bunch of parts. Be careful of those sold online however as they're all fakes; this chip was killed well over a decade ago. I'm not aware of any clones yet, though I would welcome them if on par quality wise with the original.
Whether it's actually better than those from the 80s, I'm not sure. Both HP and Philips used to use ASICs -- pretty much just matched diode arrays -- for their sine shaping, and that's about the most critical part in this kind of generator.
Then again MOSIS has prices down to a few thousand/square millimeter. Since current gen stuff is so much smaller, that's probably <$100 for the more complex chips from the 70s, & 80s.
The best I think we'll get is some Amiga/Commodore build it yourself kits That weren't possible before because of out-of-production chips.