Something like 169890 is far more memorable than 1-6-9. Say it out loud: 169, 890 ... vs... 1 dash 6 dash 9. There's a reason most of the domain auctions and services include an option to "exclude dashes" in their searches and that's because it's a nasty category under any circumstance.
You can just browse the threads here at NamePros and look to see A) who's posting want ads for dash'd names (or that allow dash'd names) and B) who's selling dashed names for any type of money. We've both been here nearly a decade and long enough to know that dashes are just the litter of the domain world. LOL!
And probably for good reason. If you have any affinity for the dash'd names, go for it.