For a replacement rear shock, I believe you could not do much better than the Wilbers.
But there's likely a strong placebo effect, given the price for these.
They custom make it for you, based upon your weight, riding style, etc. Fully adjustable rebound / preload, etc, with external reservoir.
My order, for reference, was four years ago:
--------
Product
Unit price
Quantity
Total
shock absorber type 631 Competition
Edition:
Blackline
Lift / Lowering Kit:
std
Height adjustment:
no
Federvorspannung:
mechanical (X-PA)
Spring color on request:
no
Weight of driver incl. clothes [kg]: 80
Weight of passenger incl. clothes [kg]: 70
Weight of luggage [kg]: 40
Percentage of solo mode without luggage [%]: 70
Percentage of passenger mode [%]: 5
Percentage of luggage mode [%]: 15
Percentage of passenger mode with luggage [%]: 10
Style of driving: standard
Operation purpose: Road
Item #: 631-0004-07
K 75 RT | BMW75
Year of manufacture: 1989
796,64 €
1
796,64 €
Total products (excl. tax):
796,64 €
plus 0% tax, amount
0,00 €
Total products (incl. tax):
796,64 €
Grand total:
796,64 €