I paid $2000 for my 99 E430 MB extended warranty. I negotiated $200 off from the published price with the Business Manager at the dealership. The warranty is good for TOTAL 8 years/100000 miles from the date of delivery.
If you choose to buy ANY warranty, make sure you obtain the contract and digest it first. That's what I did. I didn't purchase the warranty from the sales associate. I purchased it when I was doing the final paperwork with the business manager.