A good pair of running shoes will cost you between £100 and £200. You might decide to get a rotation of shoes for different types of run. Maybe a race day shoe, a fast training shoe, and a slower recovery show. So that could set you back a few hundred.
I've been pretty good to be honest. I've got 2 active pairs both of which I got on sale for £80.
I'm on week 5 of doing couch to 5k, but using a pair of generic trainers I bought years ago. How much of a difference does a pair of running trainers make?
Having shoes designed for running will make a big difference. You don't need to spend a lot to get some half decent ones, but they make running a much more pleasant experience.
Just to reinforce your point, the difference between a cheap running shoe and an expensive running shoe is incredible. When I first started running a few years ago, I was using a very old pair of running shoes I've had for a long time. I've since been sticking with the New Balance Fresh Foam X 880s (because I have very wide feet and NB seems like the only brand that actually makes their best running shoes in 4E) and it's like running on a cloud.
And then there's also the Garmin watch that cost $300 (that I'm now stupidly considering upgrading to the new $600 Forerunner 965), the $120 HRM Pro chest strap, the $3000 Nordic Track x22i for indoor runs I got lightly used on Craigslist for a steal at $900, etc.
And then there's the races where you're spending $40, $50, $100+ depending on whether it's a 5K or 10K or half-marathon. And good running clothes are pricey too.