Summary
The price ranges from the facets API ("Get list of the possible facets for a given query") may vary between returning buckets of "from" and "to" values with rounded prices and the minimum and maximum prices between the search results.
While the rounded prices generate a better UX to present a list of price ranges to the shopper, it's not desired to use as a price "slider".
Moreover, since the minimum and maximum prices are applied at a second moment, the price ranges as "buckets" in a search that already applies a price filter get out of bounds of bounds in relation to the specified prices.
Simulation
Using the API, make a request with and without a price filter like "/price/100:500" and observe the returned price ranges (from/to) in the "values" object for the facet with type "PRICERANGE".
Workaround
N/A