Well, it may be slightly extreme, and I've had good experiences with TK in the past, but used Riverside $5s at more than 5x the going rate? Uh, makes me wonder.
The rack of $1s is worth ~$1200 alone. The $5s can probably be had for $1.75 each (used) so $700 total for those, plus whatever the $25s (~$3) and $100s (~$5) go for. Prices are bulk and used. THis was a good deal for whomever picked them up. If I saw them in time I would've kept the $1s and spun the rest.