It’s actually quite amazing at how adding a BRU leg to almost any nonstop flight from AMS will immediately depress the price. It can almost encourage a person to just take a train to BRU from the Netherlands to catch the cheaper flight.
It is not surprising. Every other EU legacy flies to BRU (EU). SN is comparatively a small carrier (specially long-haul) compared to KLM. So KLM needs to compete with everybody else for those connecting passengers. Also BRU is not a leisure airport. In summer season there is little tourism going to Brussels, compared with Amsterdam.
are they clean, the seats comfortable, do trains arrive on time all the time?
that counts. not bling.
I agree. TGVs and Thalys can be quite disgusting. Even dangerous (I suffered thieves on board a couple of times; waiting for the police to arrive!). Nothing compared with high-speed trains in Germany, Italy or Spain which are much cleaner. Also they are very prone to delays (like German HST).
A while ago I used Thalys frequently and at some point they added an intermediary "cleaning service" (I know it because they put stickers everywhere on how they would improve the service). I assumed this would be (since Thalys are Germany/NL/Belgium/France) mostly about German customers (used to higher cleaning standards) complaining about dirty trains.