The late Gigi Sabani, impersonator and presenter, brought to Mediaset networks in the 80s a format that was very popular in the USA, a show whose title over the years has become a slogan suitable for any occasion.
And even in our sector, that of extra virgin olive oil, it is very fashionable because the price differences from one region to another are marked.
Leaving aside for a moment the shelf products (which we might talk about next time), let's try to understand why Sicilian, Calabrian, Apulian or otherwise southern-produced EVO oil has a significantly lower price than that of the central-northern regions (Tuscany, Liguria, and Umbria):

1. In the South, on average, olive groves consist of very tall trees, which by their nature and to better withstand heat and drought, are not pruned annually; in this way, pruning costs (which represent almost 1/4 of total costs) are reduced;
2. The yield of cultivars grown in the South is often higher due to the harvest period, which is often late, unfortunately at the expense of quality;
3. Conversely, in the aforementioned Central-Northern regions, the terrain is often very steep, combined with the need for annual pruning, which has a much greater impact on costs;
4. To obtain a quality extra virgin oil that lasts over time (and perhaps with DOP certification), olives must be harvested when ripening is not complete, which leads to a generally lower yield.

This explains why Apulian, Calabrian, Sicilian, and Sardinian oil is often sold at prices below €10/liter, while in Umbria, Liguria, and Tuscany prices start from €12/liter and up.
Not to mention operators who are certainly not the most honest and who sell (supposed) extra virgin oil at shelf prices, often at €8/liter.

So, if you find such offers, try asking for a complete spectrophotometric analysis report; the result is that no one (or almost no one) will be able to provide you with such certification.

Labels without the DOP seal often hide oils bottled with blends from previous years or with oils of uncertain quality from other regions.