I would look at utility modules instead of (or as much as) more modulation sources - I've typed why in multiple answers here, on muffs and on reddit recently - use google too find out why - or find my posts - I'm either JimHowell1970 or Agawell on all eurorack centric sites (reddit/muffs/here) - but I would seriously consider getting Maths - see the illustrated manual (google it) for why

I don't really think that what you've bought is "heinously expensive" though, as that implies overpriced, but definitely not cheap - it's comparable to a decent slightly over mid priced electric guitar - and that still begs the same again (at least) on an amp and effects - and lets face it how many guitarists do yuo know with only 1 guitar and 1 amp etc?

This is due to the very nature of both the market and the manufacturers - the market is tiny so you are never going to get the economies of scale that are possible even with more mainstream musical instrument manufacturers (especially behringer) and really not compared to more mass market items

Most eurorack modules sell in the hundreds - a few sell a thousand, a very few sell multiple thousands - the Lubadh I suspect might sell a thousand, but probably not

The companies that do make them are generally small and based in the first world and most don't seem to outsource manufacture to 3rd world (although I think this is starting to happen more)

Even the economics aside - I estimate I spend at least 1000 hours a year playing with my modular (not including the amount of time I spend on the internet in relation to it) - as a hobby and I spend let's say 50€/week on my hobby (2.5K/year) - it works out at 2.50/hour - which is actually compared to a lot of other hobbies very reasonably priced indeed!!!

"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia

Utility modules are the dull polish that makes the shiny modules actually shine!!!

sound sources < sound modifiers < modulation sources < utilities