Remember I cannot see the condition of what you are talking about, so you are going to have to be the judge. That unit with a bagger will definitely run over 3K new. Here are the questions you will need answers for before making a decision.
1. Have you (the dealer) gone through this unit to make it ready for the season? Yes, good----- No, beware
2. Check the condition of all belts. New, good----- Glazed, cracked, dirty, beware
3. Check the condition of the blades. Sharp, good----- dull, dirty, beware
4. Look under the deck. Clean, good----- dirty, beware
5. Drive the unit. Does it go in a straight line without constant handle adjustment, good---- wanders, beware
6. Drive the unit. 4 year old engine should sound like new.
7. Drive the unit with blades turning. Spindles should have no whine or excess noise.
8. Tires on a 4 year old unit should be in good condition.
9. Any chipping and scratches to the paint can indicate abuse.
10. Any oil under engine. Big beware
11. Any dealer warranty, good dealers selling good machines will give you something if they the unit is in good shape.
12. Look closely at the entire bagger system, worn bags beware.
13. Drive the unit, it should sound and feel solid.
14. Max I would offer 2100 if I said beware one or two times, 1900 if I said beware three or four times, 1500 if five or more.
15. Do you trust the dealer. Yes, good---- ???, beware
16. Finally what does your gut say, it's 85% reliable.
17. Let your better half read this and see the unit, sorry but they are 85% reliable also.
18. Just my opinion, many around here say it ain't worth much, GOOD LUCK