With regard to investments... I think you gain or lose what you put in.
1: to commit (money) in order to earn a financial return
When you invest money you will receive a financial return (gain or loss).
A key here is that nothing else has to be done. When you make an investment, you put that money into a 401k and it automatically profits. You can spend all the time you want thinking about that 401k, but that time spent isn't going to accrue any additional gain. Likewise, you can be happy about it (emotional investment), but that's not going to increase the balance either.
2: to make use of for future benefits or advantages <invested her time wisely>
I can invest time improving a process, so that I can perform a task more efficiently, thus saving time later. I could invest time in learning how to use my camera more efficiently, so that I could complete a shoot faster than before. A by-product would be that by doing so I could potentially make more money this way... but I can't make more money without that increase in time gained by being more efficient; spend time to gain time.
I can spend time learning to do something myself, so that I don't have to pay someone else to do it. In this case, I wouldn't have to pay for this to be done (savings?) but that time has to be spent. I can't get that time back, so was anything really saved?
3: to involve or engage especially emotionally <were deeply invested in their children's lives>
I can be emotionally invested in a relationship, in which I would hope to gain a friendship or more.
I can spend money on the person, but I can't buy the relationship. Likewise, I can sit in the same room with someone for a year (time) but it doesn't mean that we'd become friends
It's takes an emotional investment to receive one.