neumi5694: And you never know if the key from the seller is actually gonna work in the first place or - if it does - if the game will be removed a few days after and if it's even the key for the right game.
Ancient-Red-Dragon: You may never "know," sure, but you can easily make a reasonable hypothesis that the chances of something going wrong are very low, such as by gauging things like the seller's reputation.
And even if things do go wrong, which is a very rare occurrence, then you could always ask for a refund, and if that doesn't work, then open a chargeback dispute with Paypal and/or the credit card bank, etc. So it's not a big deal in the very off chance that something does go wrong, since worst case scenario, you get your money back and can re-buy the game again.
As for the higher prices you cited, I'd say that experience is atypical. Legions of people buy from key resellers because they get way cheaper prices that way; and if it didn't work well most of the time, then such businesses would not be very popular like they are.
You might save a few € here and then, but it's just not worth the trouble, I have a regular job now and my spare time has become more important.
In the US, where you need to add taxes to the prices from Steam and GOG, the "higher prices" problem probably doesn't exist. It exists in european countries where prices should be listed including taxes. The keysellers however never do so and always add them according to your billing adress.
Don't know about 'most of the time'. But I hardly could find cases where it was not like this.
Just a recent example: While Another World (steam version, I gave up on ever seeing an update for the GOG version) in the sale cost 1.99€. I missed it and a few days after that I took a look what keysellers offered: 1.78€, yay! Then the ckechout: 1.78€ + 0.44€ (Taxes) + 0,63€ paypal costs = 2.85€.
Similar things are to be seen in new games. The keyseller price is 10%(!!!) under the official price, but then you have to add 25%, which means that it's 12.5% more expensive. Only if the seller price is 21% under the price you pay on the official platform, it pays off. And - if you take in count all the sales - that does not happen all too often. I rather wait for a sale that matches the seller price. I have so many games in my backlog, time (getting a game right after release) is really NOT of the essence.