The process of heat transfer printing is very similar to using iron-on decorations. This process is not for multi-colored or very detailed decorations, but usually for a player name or number on a jersey.
With a skilled person, a good-quality job can be done. The high labor per unit makes this unreasonable for really high quantities of the same decoration, but for simple decorations that require a unique decoration for each unit (like a player name or number) this ends up being the lowest cost.
After many washings, the heat transfer decoration will possibly start to peel, but it should get through a sports season without a problem.