The B12 for a Merc (e.g. my W124 300CE) was around £550 before the sterling crash - expect more now.
The B12 is 4 springs and 4 B8 dampers and they're matched to your car - you need to choose the kit (spring rates) to suit the options fitted - sunroof, engine, aircan, radio even - the more options, the heavier the car and the stiffer the springs.
My view is that any Merc is going to need quality parts, matching the originals. You can't repair a Merc on an Escort budget - it's simply not worh it if you intend to keep the car.
The Bilstein B12 consists of quality parts that'll last long after you've got over the price. The B12 will lower your car from original height and stiffen the ride - for me, it works like a dream, even with my original, factory Sportline setup. Your installer can choose spring pads to achieve changes in the final ride height.
Another alternative is MB original parts and these can be found at discount prices but you need to work at it.
I recommend the B12 and the price is lower that MB list prices.
Good luck to you.
RayH