This time of year I am always evaluating whether to trade in my Ford. Ford new car sales are horrible so sometimes dealers are very motivated to move inventory. Combining huge rebates with dealer rebates can be very tempting.
Anyway: there was a big data websites that tracked inventory on lots that I used in 2017. It is nowhere to be found now. This goes to show that even when you aggregate lots of data it is not a guarantee that that data can actually be converted into value. After all: running servers and paying people to manage those + develop the dashboards + sell / market a service does not pay for itself.