One of the reasons I did the poll a little while ago was to test the real feelings of users on this subject. The figures I think which are relevant to you are that 25 people (18%) would be looking to buy a mod kit if available, 46 people (33%) would buy a new GP2x with D-pad integrated (same price). You could probably halve this from people who say they will to those who actually will.
It was obvious that the vast majority of users are unwilling, for various reasons, to open their GP2x and do any mod - anything more than removing a joystick cap and replacing it does not seem viable to many - fair enough. Put it this way, my mod did not require any special skills to make it and didn't even mean clipping off the end of the joystick stick (if you didn't mind the end product being slightly higher, which still isn't an issue to use it, BTW). Wow, big deal - no destruction, no sanding the front down (if keeping the stick intact, as opposed to the way I did the mod). Anyone could easily have tried this mod, and if they wanted to, could revert things back to how there were (ie lifting off the D-pad mod from the case, not leaving any marks on the case), removed the joystick from the motherboard and done your/other D-pad mod. The fact that no-one at all did this indicates an unease about doing an internal mod - which doesn't help with your project!
Those people who have the ability and desire to do so can already make their own D-pad mod - there are many step by step guides for doing it with a GameCube D-pad, NES D-pad and a make-your-own one. The principles are similar - the only real difference between them all is keeping/removing the stock joystick and using a controller PCB or not.
I rather suspect therefore, (I believe my comments are impartial and constructive - I am not selling anything, far from it, so I have no personal motive - I am trying to give an unbias viewpoint here) that people who can do the upgrade already have. Those who see further "how to" guides/instructions will also have a go (parts are easy to get hold of after all). You are then left with two categories of potential customer - those who want a pre-made D-pad and happy to do the mod as required (limited numbers, but that is your market); and those who want one but only if they can have one done from them. This is fine, but as the comments show, they aren't expecting to pay much more than stock cost for this; which doesn't cover your costs, or profit. To make it viable, if you say it costs about $200 for the unit and about $15 for the kit and $200 for the GP2x, you probably will spend a couple of hours doing the work (start to end) per GP2x, to make it worth your while I guess you are looking at selling for about $270 minimum. The reason you posted this "how much would you pay" question is that you want to see what people are prepared to pay before pricing yourself out of the market - no other reason, which is fair enough, but from the comments on this thread, it doesn't appear that people want to pay more than costs - so no point.
You also stand to ruin or mark some GP2x's which will make them unsaleable (and come off your profit line), but even more relevant, is YOU then become responsible for the guarantee period. You cannot sell anything new (second hand is fine, but you will not maintain a "as new" price", rather a discounted price, which defeats the object here) without a guarantee (1 year), so even though you send the GP2x out after testing it, if it goes wrong, you have the costs and issues to resolve - also it would be hard to prove that the problem was the actual GP2x and not your mod - so you will be liable. The only way around this is to sell "as is" without guarantee, but no-one can see it "as is" before buying, so it is on trust - however no guarantee, cheap price (why should anyone pay full whack for something without any guarantee?), no profit, and after-sales issues.
I really suggest to you DaveC, that you can only offer to sell mod kits, with the disclaimer that people undertake the work at their own risk. You would be giving yourself major problems if you don't. You are unlikely to sell many units at all really, unfortunately (I would prefer that your venture was successful, I add, but I am being realistic here), based on what we know so far; how about stating a final sale price (inc shipping) for the D-pad install-it-yourself mod, asking people who positively would buy to send you a PM as a pre-order intent, you then know exactly how many to make and how profitable it would be. You can then post the results. (Just a suggestion).
