Maybe a tad steep but if there are no cracks on the handle and none of the teeth are bent, well that puts it distinct from the vast majority of the pack that you'll find on the usual auction sites for prices not a great deal lower than that.
If it's really grubby, it might be difficult to judge its condition, and £37 would be steep for a cat in the bag.
But if it is in a decent shape, it might be a good buy.
I was thinking of selling my Techs, though, and one of them should be an all brass one, so if you'd like, I can lend it to you if what you're looking to do is try one out.
If it happens to be a different Gillette head on a ball-end handle, I might have one or two around as well.
Yes, $9.99 but straight away in similar items, there's another one for £60. It's not unusual for a £25 to £50 buy it now in very tatty condition, nor is it unusual for a £4.99 starting bid which will go for the first bid ... but, the items do need to come up and they're not infrequent, but they're not that frequent.
I think as with many such things, if you want one now and see one ... pay the price, otherwise you can wait.