Greetings
Treet SE blades are carbon blades whereas the blades that Connaught sells are Stainless steel with a PTFE coating on them.
GEM Blue Star are another popular carbon steel blade, both of these blades are only sold in the USA and the blades on Amazon come from there.
Ed (Monkeytennis) very kindly sent me some Treet's to try and I found that they are only a two shave blade and I would only consider my beard to be medium. I understand ED does better with them than I did. I did better with the Gem Blue stars; I found they lasted for three sometimes four shaves but again they are only available from the USA.
Both of these carbon blades need to be removed from the razor and thoroughly dried, they will rust overnight. They should not be stored in the bathroom.
Carbon SE blades shave very well but have a slightly different feel to them, they do not glide across the skin like a coated stainless blade, this is (IMHO) nothing to do with the sharpness and everything to do with the coatings modern stainless blades have on them and the fact that we are just not used to shaving with uncoated carbon blades as our fathers were.
Carbon SE blades are also more expensive than the coated stainless blades from Connaught's so there might lie your answer.
Regards
Dick.