JAileen, I know you asked elpgal, but since I also have a Miele I pay around $20 for a 4pk of bags which includes a motor and air filter. One bag last me around 4 months. But I do everything with it. If you are strictly looking to only vacuum rugs and floors, you may want a less expensive option. I love the Miele because in addition to the floors and carpet, it comes with a dust, crevice, and upholstery tool. I also bought a long flexible crevice tool so I can vacuum under the furniture, behind the cabinets, washer and dryer and can even vacuum the internal dryer vent.
So essentially I use this one vacuum to do everything in the house; floors, rugs, stairs, drapes, window sills, doors, baseboard, furniture, frames, fireplace, etc. Unfortunately, I think my particular model has been discontinued. The other nice thing about the Miele is that you can buy HEPA filters if needed for those who have allergies. Best thing to do is to find a store that deals strictly with vacuums and get their suggestions. They usually have display models in the store that you can try out. They even give you loaners if your unit is on the fritz and getting fixed. Luckily, I have a sewing and vac place near me which serviced my old Electrolux and got me a new power head for the unit.