Aser beshvil shetisasher is only true for maaser peiros. It does not apply to maaser kesafim, which is only a minhag according to most poskim. the gemara in shabbos 119b says that the ashirim in eretz Yisroel are rich because they give maaser peiros. It says the ones in chutz la’aretz are rich because they honor Shabbos. It does not say because they give maaser kesafim. I’m not saying not to give tzedakah. I’m just saying you can’t test Hashem based on this.
I know someone who made a lot of money in the stock market during the tech bubble. He gave maaser and lost it all (900k), except for the maaser. when he spoke to a gadol he was told that either he’ll make it back or was chayav misa and this was in place of it. He still didn’t make it back, and according to my rav, there was never a guarantee anyway. Mitzvos don’t hurt though.If you don’t get the sechar in this world, you get them in the next.