Thanks for the responses guys.
I think pricing is always a tricky thing to judge, but bear in mind a LOT of work is going into this to make it right, yes you can reverse engineer the sounds - that is part of the idea, but also I'm aiming to make the sounds very suitable to use as-is, a 909 type snare for example - most of the work is getting the correct time response of each of its components, once you do that it sounds 909ish, the scope then is for user tweaks is things lke noise level, tuning, decay.
I'm a big fan of tutorials, even done more than a few myself, as well as free kits, but this is something different, think of it as a time saver - I don't really expect everyone to load up 128 of these sounds into their machine and start sounding all the same, the idea is make them your own, view them as shortcut templates for your productions. Remember I am going to have documentation describing each sound - this is NOT going to be along the lines of 'how I made this sound' but rather a description that tells you what it is, and perhaps suggested tweaks, a few lines of text for each. So you can read through the doc and choose which to load, rather than having to clear the machine and load in the whole bank.
Now, one more thing - would you guys prefer that I stick to the original idea of 128 drum sounds, or would you prefer to have say a 50/50 split with other sounds like leads, basses, pads, etc? Again if I went this route I'd focus on mostly staple 'bread and butter' sounds rather than distinctive niche sounds that sound impressive but you'll never end up using.
Thanks for the input, I will get back to PMs in due course