Guardian angel was added due to a large amount of people having connectivity issues, it was something you could spend your money on to not lose your stuff at GWD if you dc'd. It's definitely a positive feature for a lot of people. It used to be 1m cash and later was put into the donator store for 200 donor points, it has already been made a lot harder to get your hands on a GA. You still lose your GA and have to buy a new one from the donor store or other players if you die, whereas if you died without a GA, you could have gotten back to where you died and picked up your stuff. The pros really outshine the cons here.
First off, I'll mention something that is literally always mentioned when people start discussing prices and still somehow always forget. Prices are entirely controlled by the players buying and selling the item. Prices depend on supply and demand. A lot of people go to gwd, many need bandos armour, the godsword however isn't needed all that much. Back in the day people would legitimately train their stats using a godsword as a main weapon, now that we have dragon hasta (basically a whip that can train strength) people don't really seek alternatives anymore and the popularity of using them as a mainhand weapon decreased. If you wanna use it as a spec weapon to lower defense, statius warhammer outperforms it. I think you shouldn't compare the two economies, too many things have changed for that.
They are so low for a few reasons. Rare whips aren't stronger than regular whips anymore, people often still use abyssal whip or d hasta over a donator whip. They did get some compensation though, the attack requirement was removed and the stats now scale with your attack level, up to 70. Donator system was changed and some items are a bit cheaper. Probably the biggest impact on it is that there are no item sinks for the donor items. More people donating means more supply of donor items while the demand doesn't really increase, this causes prices to drop.
Like that person said, making money is easy, it was in scape and it still is now. Not to judge you for wanting to donate for bank, but you should only donate because you want to donate to the server. If you want money for your donor points I'd recommend getting GA tickets and selling them, they have the most value per point.