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OK, so you can spend money on lighter shoes, gym classes, physios, training books and accessories, coaches etc. but it is very difficult to prove how much each of those contributes towards making you faster.
In a cycling timetrial, wind tunnel tests show that over 40km (around 1 hr ride time) the best skin suit saves 134 secs; aerobars save 132 sec; aero helmet 67 secs and the list goes on. Therefore it is pretty much possible to work out how much each second improvement would cost your wallet.
So if you could buy something (a pairs or shoes / physio time etc) with a guarantee that it would knock around 5 mins from your 10m time or 15 mins from your Marathon time, how much would you pay for that?