These costs trickle down to end users. Even in "progressive" (heh) South Africa 3G can cost as much as ~$150 per GB (so called "out-of-bundle").
I was attempting to set up IMAP in Thunderbird for my parents (who are forced to use 3G due to location) - the obvious merit there is the cloud backup of their emails. To conserve bandwidth they previously had POP3 set up to download headers only. This is impossible to set up with IMAP because, according to Thunderbird HDD space is more expensive than bandwidth and hence re-downloads items if you choose to have headers only. This is a well-known piece of software.
Keep the high costs of poor little Africa in mind when designing your software. Many of us are lucky enough to have access to "high-speed" 10Mbps uncapped copper but there are significant amounts of people who are outright extorted by the cellphone networks.
Please design your software to be kind with bandwidth. Latency isn't the only issue and, in fact, of all the people I know only gamers care about latency (because we have the bigger bandwidth/speed problem to deal with). The average African is quite happy to wait 1s for a website to load, they aren't happy if that page costs them $1 to load.