Churches are financed by donations from their members, and are generally prohibited from engaging in business enterprises to make money (except on a small scale, such as car washes or bake sales). Lots of people give lots of money (and time, and energy) to my church, and just as new people frequently join, existing members occasionally leave. What's odd is when they ask for a refund.
It should be pretty clear that, as a practical matter, a church can't make a practice of refunding money to unsatisfied members or former members. Where would the line be drawn? If someone has been a member for 50 years should they be able to get all their donations refunded if they decide to leave? Although money is fungible and it would be possible to give refunds on a small scale, it would be impossible to fairly extend the practice to others once the ice was broken. (Not that many people would ever ask for such a thing, no matter how dissatisfied they were.)
As a theological matter, I don't think God gives refunds. In reality, we never give God something that he didn't first give us, and nothing we give to him can ever measure up to the gifts he's given to us merely through creation. I think most Christians would agree with this. The benefits we should expect from giving are spiritual, not material.
However, I can imagine that if a person leaves a church after giving money for a long period of time it can feel like they're abandoning a financial investment, but that's really the wrong perspective. When we give money to a church we aren't "buying into" anything or building equity. The money is given away, and it's no longer ours, and we get nothing in return. The church serves everyone equally, regardless of how much they give or how much they need, and no special favor or regard is obtained by giving a lot. For the most part, very few people know who gives how much -- generally just the treasurer, for tax purposes; our pastor doesn't know who gives what (although I'm sure he can make reasonable guesses, but so can anyone).
Apparently, God also doesn't finance cars.