Identify the existence of a wall like structure in a given int array

The idea is that I will query an API endpoint which will return me an array consisting of a price value and a quantity value [price, quantity].

In this dataset there is high possibility that there are structure of values where there is a sudden increase in quantity for a given price range compared to the rest of its surroundings, basically a wall like structure.

Example below shows a range of price values and a quantity value as a heatmap. If I were to get a dataset of this area, I am interested in identifying the large, light colored, wall like structure. I have thought about brute forcing for every x amount of price and trying to find a sudden change in quantity and later try to look around it to find the extent of this wall but this just doesn't feel like the right approach to me.

Is there any other algorithm or way that comes to mind for searching for this kind of data? Consider that the dataset is small enough to fit into memory and there is no rate limits for pulling from the API.