Sometimes people call me crazy, but I always calculate the cost of "weird currencies" - be it in SL or in games etc., where they invariably try to conceal the actual cost of their digital wares by making you first buy a weird currency and then spend that, rather than "real" money, for whatever they peddle.
It's something I will always recommend - not that you shouldn't spend whatever you want on your hobby, but it should be an informed choice rather than letting yourself get tempted into spending more than you should. I detest that companies live off this.
At the very top of my "SL notes", I have the calculated cost of various amounts of L$, so I know that when I spend so-and-so many L$, I actually spend so-and-so much -actual- money.
I calculate it by initiating a purchase of a realistic amount of L$ (for instance 5000), the viewer then tells me what that would cost in dollars, I ask Google what that would translate to in my currency, and then I divide it by 5 to know what 1000 L$ costs, by 10 more to know what 100 L$ costs and so on.