I daren’t add up what I’ve spent…..
It all depends on your background and what you have access to elsewhere (e.g I wasn’t a welder but had other metalwork and engineering skills and access to gas torch and bottles after hours at work). If you have similar then in theory materials is about £150-200. Vee blocks and a flat surface can be used for a jig. Free tube notch templates and cad on the Internet. Drill, hacksaw, vice and files. Brazing rod, silver solder and good fluxes.
But then it is much easier with a jig (so that needs making first).
And a tube notcher jig is handy.
And maybe tapping and facing tools.
A home oxygen generator / propane torch is convenient.
Then maybe some tapping and facing tools.
Expanding reamer for seat tube.
Somewhere fireproof to work…
As you can see it never stops.
Damn those courses with full equipment suddenly look cheap 🙂