Small point of order - While the league was conceived as part of their conditions for hosting the World Cup in '94, MLS didn't kick off until '96. Your overall point is correct, however. It is the variety of spending controls that has helped lure investors knowing the league would strive for a sound business model. It was as recently as 2003 (IIRC) that the league had just 10 teams and a league average attendance under 14,000. Not exactly a formula for winning sponsors and media dollars. By keeping team costs manageable and emphasizing investments in the facilities and, eventually, the academies MLS was able to build their product.
The '94 World Cup was the beginning of the league, despite the fact that they didn't kick a ball in anger until '96.