Considering that in Fallout 3, and I'm pretty certain, Fallout 1 and 2 as well, it was impossible to go over the cap even with items that increase your stats, I'm guessing that the same will be true for New Vegas, I wish they'd change that, though, it really doesn't make much sense, why would power armor suddenly magically stop enhancing your strength just because you hit an arbitrary limit on it? I understand capping the base stat you can have, of course, but not letting one get past that limit even with items just seems stupid. Plus, it makes it so that stat increasing items are utterly meaningless if a stat is already maxed. Some might argue that it's set the way it is for balance reasons, but that logic assumes that Obsidian would balance the game with the assumption that players will NOT use items to increase their stats beyond ten, which makes no sense, if players can do that, then one would expect the designers to take it into account with game balance. And besides, it's not like you could infinitely increase your stats. The amount you could increase any stat to would be limited by what stat increasing items exist, so in the end, how high you could get your stats would be limited, it's just that then, you might actually have a reason to sacrifice points from stats you have less need for to raise ones you will need to 10 instead of 9 since items that increase your stats will still be useful even if you have ten in a stat. But obviously, it's too late to make changes like this to the game now.
Just checked the F2 wiki and those implants had no limit. But there were only 4. I also heard the FNV implants get extremely expensive, but no specifics. My guess is they will increase in price each time you buy one.
Well, if we go by Fallout 3, and in fact, most RPGs I've played, the price won't be much of a problem in the long run, especially when you consider that for an unspecified high price you can gain a permanent increase to a certain stats, so if there isn't some other limitation on them besides price, I'm not sure how much difference it will make.