I think it was circa 2012, and I may be exaggerating somewhat, but I particularly remember seeing new, lots-of-option Kia Souls selling for ~$18.5k new (window price) right next to used ones going for ~$18.5k used (window price) with nearly the same options on both. I think I also saw something similar with a few models of Honda, but my memory is most vivid with the Souls. And if memory serves, even when used was cheaper it was often not a whole lot cheaper. I also remember at least one dealer marking up all their new cars in the $17k to $25k MSRP range to new MSRP + $5k, and interspersing them with used of the same model at new MSRP (obviously sticker price is
supposed to be negotiated, but it was still kind of ridiculous).
I think for the most part there just weren't very many quality (workhorse model, a-la Prius, Civic, etc.) used cars for sale in my area at the time that weren't 4-ish years old or more or which didn't have more than 64k miles or significant and obvious problems.
And yeah, interest rates on new cars loans were sometimes sub 1%, rarely more than 2%.