It's worth noting,that the price on the Tracy site,is for Carbon Steel.
HSS tend to be around double the price if you contact them.
I used a friends tracy tools carbon steel taps to cut some cycle threads in 300 series stainless steel and was very surprised at how well they cut , no bother to them at all.
dunno what u have been buying. ive threaded a lot of stainless steel with carbon steel taps and diesThat's impressive.They must be better than the average.
Those "re-threading" taps you can get,are carbon steel,they'll clean out a thread,but won't cut a new one even in mild steel.
a good set of carbon taps and dies up to half inch would cost 60 quid