I obtained a lockbox on my Paladin, so naturally I wanted to get it opened. Sure enough, a Rogue (named Forgh) answered my request for a lockpicker.
However, when it came to the tip, things went downhill rather quickly.

He’s telling me that I will get 30 gold and an item worth 5 or more gold in the box. To me, this implies that he doesn’t like my tip, and that this is a hint for a bigger one. So I decide not to bother.

When I said ‘attitude’, I meant that I didn’t like how he was asking for a bigger tip. If he wanted more gold, all he had to say was ‘thats not a good enough tip’ (or words to that effect). But no, he decided to be smart and try and hint his way to getting more gold out of me.
I don’t mind giving people a bigger tip if they ask, but when they do shit like this, it is my belief that they don’t deserve it. So, I put him on ignore and found someone else to unlock the box for me. Mindful of what had happened with Forgh, I tipped this person 10 gold, my absolute tip maximum.
There’s a lesson to be learned here. If you want something, ask for it. Hinting doesn’t get you anything.
I should point out that Forgh was in the same guild as Boltsmore (AKA Boltsalot). That’s why this is filed under ‘Guild’. I quit said guild after this incident.