All 3 of our ST1300,s are fitted with Givi 55's c/w mounting plates & the top case rack, an excellent product.
You are right, not much change out of $1K each but we have found them brilliant, well worth it.
And the size suits us to a tee for 2 up travel with tent, airmats, sleeping bags and groundsheet all in a silver Ortlieb bag on the rack. If the weather is looking dodgy on the day, our wet weather gear when rolled up tight fits under the outer duo strap of the Andy Strapz if reqd. The A S,s are another great product.
Std Givi Red, Silver or Black also match the ST colours so the whole set when loaded onto whichever bike still looks the goods!!
Cheers
Neil
NandV