Running

I was actually also surprised on how much i ended up spending on running when i got more serious. But in the end it is a hobby and that simply comes with some cost. I dont think yours are actually outrageous.

The races are a big event and relative to that i actually doubt you'd spend less if you were to do some other larger all day events.

The clothes you'd likely need for any type of sport (which you can also see as an investment in your health) and should usually last quite a while.

Tech wise i think your 3 year old garmin should hopefully have a bit more life left and the HRM should also last quite a while (and isn't that necessary imo)

The two big dials where you can imo adjust your spending are coaching and shoes. The first one would be a reoccuring cost and the second one is the main "consumption" type of equipment of the sport.

A coach can be nice as source of motivation and to hold you accountable, but as an amateur runner we still have so much room to improve that we can get more than enough out of just following the average proven training plan.

As far as shoes go some costs cant be avoided, but they can be limited by holding out for good deals and using good value workhorses for the majority of mileage (only doing the key sessions with your better pairs). You can definitely find sales on good durable daily trainers like the puma velocity nitro, nike pegasus or saucony ride for like $50 per pair.