The article refers to one device from Apple vs tens from Samsung. I think it would be fairer to compare with one device, such as their most popular one.
Why would that be fairer? Apple chooses to compete in the market with a clear lineup of 3 device-classes that each have multiple models differing in the amount of memory only. They don't offer low-end models. They obviously think that this is the better strategy. Samsung thinks it is better served by building more models to serve a higher range of customers. It is perfectly fair to compare which strategy fares best - and by number of units sold Samsung seems to be ahead. By revenue, Apple seems to be ahead. Whether that balance is going to tip is an interesting question, but it's not answered in this article.
Unfair would be to compare the number of macs sold vs. the number of android phones sold since those devices don't compete against each other on the same market.
The 3GS is apples low end model, that doesn't mean it is low end compared to other models on the market. An 8GB 3GS sells for ~ 370 Euros. That price may be a bargain for that model, but I can buy Samsung phones much much cheaper.
Edit: Response to the parents edit: Yes, your view is US-based. If I buy a phone and get a phone contract without subsidy, my contract is cheaper - up to 10 euros/month. I'd be surprised if that's much different in the US - you always pay for the subsidy in one way or another.
Any phone with a 480x320 screen and free on contract (at least in the US) is low end. The iPhone 4 would be midrange and the 4S would be high but not the highest end.
The 3GS is not free on contract in Germany. Fact is that there are cheaper phones and that may be of importance in markets where the average wage is lower than in the us. And since the article is about world-wide number of devices shipped, that makes a diffence.
You said the 'article' was misleading.