Ah then I was very wrong, you are in fact a bit older than me :)

Thanks for teaching me a new thing about life outside of the US. Out here, cell data plans (which is the budget that sending/receiving MMS would eat into) were relatively affordable (even for my somewhat modest household) through the latter half of the 2000s and early 2010s. And now it's basically assumed that most people have "unlimited" data. So I guess MMS was a regional phenomena based on prices.

You didn't miss out on much, not that you probably thought you may have. MMS was a useful tool for sharing pictures digitally, but it was somewhat poor user experience waiting for it to reach the other person. Sometimes waiting for a reaction for an hour because the person on the receiving end wasn't near enough to a cell tower owned by their provider. Less of an issue with all the cell towers around now, but there are better mediums than MMS now.

Until 2010 I worked for Route Messaging (now they are called Telesign) on internal systems as well as integrations with mobile operators and other "messaging brokers" around the world.

MMS was indeed order of magnitude more expensive than SMS and several orders of magnitude less used.

Reasoning for such high prices was more about mobile internet/data back then being really expensive "1G" - and MMS was (still is I guess) using mobile data to send/receive "multimedia messages".

At this point I expect that cost of MMS is more about maintaining legacy systems/servers for that.

Although in something like 2008/2009 integrating through legacy SMS protocols (those previously used by beepers/pagers) was cheaper than through modern protocols. Some operators had hardware boxes supporting those that were already paid off long time ago.