Haven't done the same comparison with other catalogues (e.g. SG, Mundifil, FACIT, NVPH), but will at some point.
I have been looking at some of the more expensive Dutch sets. There are some very expensive sets issued in the period 1940 - 1955. One such set is the 1949-1951 permanent series known as 'en face.' It is catalogued by NVPH at ca. € 350 (low values) and € 1,300 (four high values). You can buy the low values for € 75 - € 100. The high values will set you back € 200 - € 300. I regularly see these offered by Italian sellers at around € 600 and US sellers at € 800 - € 1,000. I doubt they will be able to sell those stamps.
I have seen similar instances for the Queen Wilhelmina high values set of 1946.
As far as international markets go, for my own area of interest I am not convinced. Non-British sellers often are completely incapable of correctly identifying watermarks and even simple things as discerning between Spanish and French currency overprints for the Morocco Agencies are too difficult for non-British sellers.
Also, if I buy an expensive set of Dutch stamps abroad, I get charged 22% import duty. When I buy it from a seller in the EER, I do not.
You might also struggle to find certain stamps outside the home country.
It is international but with a lot of obstacles.