You only get the sacrifice bonus once per ETB
The ability to ramp without losing out on too much mana can be very powerful
That said, a few do make it into the BAE
Saproling Token (Invasion) Sliver Token (Legions) Soldier Token (Onslaught) Spirit Token (Champions) Price $4 to $8 Median (there are significantly more Sliver tokens on the market than Saprolings, Soldiers, and Spirits) I would say all the above tokens are collectors items, with the most notable being the Sliver token and colorless Spirit with no abilities (which is produced from Forbidden Orchard)
If so, where would you put them
Beyond that, efficient cheap creatures should be slotted into "strong filler" while unexciting expensive creatures and the bulk of noncreature, non-removal cards should be slotted into either "weak filler" or "mostly useless." Early in the draft, any time you're in doubt of which card to take, err on the side of taking the cheap creature