It is all relative..
1) If you're in the market for Satellite Internet you must assume you're either off telco & cable grids, or stuck in the 56kbps dialup, 64kbps single channel isdn, 128kbps dual channel isdn, if you're on the more fortunate side of this hypothetical, you'll probably have 786kbps - 3Mbit/6Mbit max ADSL. perhaps some obscure niche WiFi territory with the addition of 'middle of no where style' 3G reception. 4G at this time be it LTE or WiMAX is almost surely not within this infrastructure geographically limited marketshare.
So basically what it comes down to for these poor but still significantly large sparse geographical market is if you're in ADSL range, or wired with doscis. If not? Guess you're going to be enjoying your Satellite Internet for 'broadband' and perhaps a 56k dialup setup for low-mid latency gaming. (ISDN being the best low latency side-kick to the large throughput of the Satellite) given a combo like this you are probably doing just about as good as you could do given your restrictions, bulk data transfer via ISDN so you don't eat into your tiny 20GB cap (though cellphones are typically capped at 4GB to put it in perspective).
Now why would they try to compete with only a 20 GB limit ? Well you see Satellites are a hugely expensive single structure, its quite different from the transfer quota any other type of infrastructure can provide. Satellite = Few Transmission Systems, but forced to handle a much much larger percentage of subscribers on a single 'node' if you will, and in this situation you can't simply launch more satellites, or add upgraded switches to the satellite so they can't go with the oversell your infrastructure route, they simply are matching who matters, their direct competition of other satellite carriers. Because like I first pointed out, if you're shopping satellite, you're typically doomed anyways..