Bro jab aab jao tou first ask ke kitne ka lga ke do ge muffler. Don't show him my bike's muffler pic otherwise he will know ke I have send u and will quote u around 3.5k
So just act normal(not very interested) aur jitna ho sake kam karwao. Give ure best offer like 2.3k /2.5k (whatever u r OK with) and tell him ke iss se zada nhi de sakta. If he says ke nhi it's not enough then u simply say ke Theek bhai main kaheen aur se check kar leta hon. Believe me wo aap ko wapis bulwae ga aur apke offer ko accept karle ga. Uss ko tou kaam chaiye.
And one more thing, settle karlena ke paint bhi isi price main kar ke de wo. Mera mashwara hai ke powder coating karwa Lena. U can ask him for details for powder coating. He will guide u.