(A) Do not make trades like this on GW2 unless you 100% trust
(B) Always devise a witty backstory to you trade, outside of the GW2 environment "never using in-game text boxes", that references something that has nothing to do with GW2
such as: attaching a note on the e-mail when you send the gold that says something vague "Thanks for helping me build this site"
That's something that a-net cannot prove or disprove
(C) If any problems occur during the trade, make sure the other guy sticks to the story
But 7000g in one go is too much
That's too obvious that e-currency transaction is happening, regardless of how you play your transaction
The only way you could cloak such transactions is if you were the leader or were sending to the leader of a large guild 500+
and made it look like some kind of donation towards a guild event "such as TNO 1v1 contests that fund large rewards for 1st/2nd/3rds"
See, in the above situation you could have ticketed a-net and told them "Hey, I sent 7000g to help fund this guild's reward pot and got banned?"
Your chances of solving the problem is much greater with a coy allaby