It has taken me some time, but I have done some research on the topic and compared the prices of some chocolate, deodorants, and spirits. What did I discover?
In general, Budapest Airport is more expensive than the cheapest options you will find in Budapest or ordering online. While a Milka chocolate of 250 gram will cost you 5 Euro at the airport (2000 HUF), the price of the same chocolate in a grocery store is between 2,5 and 3 euros.
If you want to buy Unicum, the traditional Hungarian herbal alcohol drink, the price is closer to one another, but it is normally cheaper to buy in Auchan, Tesco, or a similar store compared to the airport.
If you want to buy Hugo Boss perfume, it is still cheaper to order online or buy from a somewhat cheap perfume store in Budapest.
All in all, it is cheaper in Budapest, but if you find something on sale at the airport, there might be money to save.