if u feel that the seller is being rude or unreasonable, walk away: there are thousands of basses in sg. it also helps to find out the prices of the instruments u r eyeing on at retail (pre-owned) - u can then extrapolate the reasonable price to pay via depreciation of the axe for every yr or something like that. however, if the axe is rare then it may appreciate

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i had a supposedly 'old bird' here who tried to sell me a bass that is 3 yrs old at ard current retail price. he got pissed when i pointed it out to him and was really really uncivil and even used the f**k word....so welcome to the club.
last, when u quote a price, some jokers here will accuse u of 'lowballing' when in fact he/she is also 'high balling', go figure. i was accuse of this even tho i hadn't even made an offer

. in short, it can be an adversarial process but i'm sure there are nice sellers out there. i had a pleasant experience with a seller of an srx500. even tho the deal didn't go thru, it was amicable.