used screen printing equipment

i am looking at buying some used screen printing equipment. i originally was looking at a small set up with a table top press at least four colors. but then i stumbled upon a set up that a guy is selling that has the little buddy dryer ad 6 color riley hopkins press, flash dryer, and exposure unit. i believe he bought it from silkscreeningsupplies.com in which case it runs around $7500. he has had it a year and only used it a couple of times. it has been in storage for about six months. he is asking $5500 i was wondering how you know how much it is worth and how it i figure out how much to offer. does anyone have any advice on this. any thoughts would be much appreciated.