Rubies are Red Corundum. They belong to the same family as Sapphires. Most people think of Ruby as Red and Sapphire as Blue. What a pleasant surpirse they receive when they find out that Sapphires come in orange, purple, green, black, yellow etc and Rubies come in a myriad of Red shades like pure red, orangey red, pinkish red, brownish red etc. Nature's factory is fun & quirky!
To a color scientist, there is no Pink. Technically, Pink is Red at a lower saturation. Using this logic, there should be no distinction between Ruby & Pink Sapphire. Think about Blue. We don't have a special name for light Blue Sapphires.
However, the market reality is that we do make a distinction between Rubies & Pink Sapphires. One of the reasons is because Rubies usually command a higher price than Pink Sapphires.
Where do we draw the line bewteen a Ruby & a Pink Sapphire? In general, it is b/o saturation levels. Higher saturation reds are considered Ruby. Lower saturation reds are Pink Sapphires. However, having personally handled stones of superb saturation that would still be considered to be Pink Sapphires, I would have to say it's best to use your own judgement on a case by case basis.
To make things even more interesting, perception also varies from country to country. Many Pinkish Red Rubies (so favoured by the Japanese) are called Pink Sapphires by Americans.
Should you buy or not? If the price is fair, and you like the look of the stones - go ahead!
Hope that helped! Good luck, Ryan!
Me - I'm a gemologist and a part-time gem dealer.