I will assume you are talking about male scholarships. If the goal is just any amount of money, it would be the decathlon in track and field. This is because a lot of time you find an athlete that is a decent sprinter/jumper who wants to compete in college, so a coaching staff will tell them if they are willing to do the decathlon they could have a spot or a little money.
Next to that it would probably be lacrosse because it is a newer sport so the skill set has probably not developed completely, but although there are 12.6 scholarships, not as many schools have it as some other sports so it may even out with a sport like men's golf where there may not be many people on the team but almost all schools have a men's golf team. Wrestling may be a good shot too because a lot of schools do have wrestling, especially some smaller DII and DIII schools.
Track would be the cheapest because a lot of coaches just want to see a kid is fast and has decent ability in the other events, showing that they could be coached better. So more time can just be trained on speed work and strength training. If an athlete already has perfect technique from years with a private coach it may be a turn off because to college coaches because they may not see ways for them to improve quickly.
Cross-country/track & field – 12.6
Fencing – 4.5 for men
Golf – 4.5 for men
Ice hockey – 18
Lacrosse – 12.6 for men
Skiing – 6.3 for men
Soccer – 9.9 for men
Swimming and diving – 9.9 for men
Water polo – 4.5 for men