I really like the OPs thoughts on this. I would like to add a few thoughts of mine, too.
Now, as english is a foreign language to me, I beg for pardon in advance if some sentences end up incomprehensible. Just tell me, and I try to clarify my thoughts.
One thing to consider when talking about giving customers an incentive, is that customers, themselves, tend to be 'greedy' - we'll try and settle for the best deal, and one might compare items one could gain with MC with items outside of MW:O. This is because, well, everyone wants to make the most out of his/her money, right?
Now, I can only speak for myself, but I would have bought MCs already
simply to have them ready in case I really want something. However, I feel spending 10$ at once is a bit too much to spend 'for the sake of spending'. For 10$, I can have a nice evening with my friends, meeting somewhere and ordering a pizza or something. For me, at least, RL trumps videogames. IF there where a 5$ option, however, I'd compare that to a pack of cigarettes. I'd have to choose, fun or smoking. Clearly I could smoke less this month
It's about having options, and choice. By offering different options, people can make 'their' best choices. Also, 10$ is a tangible amount, simply by having two digits. 5$ much less so. And I could see myself spending that amount repeatedly.
The 'lowest priced' offer also serves as a threshold. As it stands now, PGI doesn't seem to want my 5$, simply by not offering to take it. Now, I
could save up my money and take the 10$ offering, but then my expenses become tangible again. 5$ are spend very easily, and personally,
I would probably spend them more than twice as frequently than 10$.
Simultaneously however, PGI understandably wants people to spend money in a 'the more, the better' fashion. After all, if a player is ready to get his/her wallet out, you'd rather have them spend 15$ instead of 5$, for example. And here, I would play on the customers 'greed' - with bundled offers! This is already considered in the 'buy MC' page (and I could imagine MCs are spent quickly
once you have them), but you can do this in your ingame store, too. Having incentives to spend money is good, but having incentives to spend
more money is also good, and I think one can make people spend more money with the prospect of saving money.
For example, if the 'Buy MechBay' Button would redirect me to an ingame store, where I can pick and choose between severel MechBay offers, let's say 1000MC for four, 600MC for two or 350MC for one, I am confronted with a choice of how to spend my money. And I want to make the most out of it. I might want to spend only 5$ a month,
but I can save about 3$ by spending 8$. But I can't buy 1000MC exaclty, only 1250MC, so I'm left with 2$ spare
that now belong to PGI. I'm not planning on spending them, but now that I have these 250MC loose in my pocket, maybe exchanging XP to gXP isn't so bad, after all? Can't change em back to dollars anyway.
At the same time, those that can't or won't spend more than 5$? They have the option to keep within their limit, and more importantly, their money is still welcome.
Well, these are my 2 cents, hope they have some merit