Well we all know how annoying it is when a neighbour tries to get you to lower your price at the flea market,and I expect we'd all love to know how to get up to 30,000 bells of one neighbour!
--Well you can't so HA!--
Joke! Heres how:
Go fishing, and try to only catch BIIIIIG fish! (Hint set your clock to 1-4 am-ish and fish in the ocean to see if you can catch a shark! You'll know its a shark by its big fin!)
Next step, once you have caught several fish clear your room and place them in it. Then the next day,(or whenever the flea market is) Neighbours will istantly be attracted to the fish, start your price at about 10,000 bells and if they're happy to pay that then get as high as you can, like I said for some rare fish they will pay up to 30,000!!!
btw this will work with bugs but only rare ones! once again time travel to 1-4am and make sure you have at least 3 coconut trees! There will be some very rare bugs on the trees! If the animals arn't interested then Tom Nook will pay from 6,ooo-12,000 bells for them!!!