I finally bought these strings after years of reading extremely positive reviews about them. Bottom line,,, can they really be THAT much better to justify the relatively high price. Answer - ABSOLUTELY!
My main 4-string bass is a 'FrankenFender' with a trashed Jazz body, beautiful 1960 P-bass neck and S.D. Active e.q. pickups. Always loved this bass, but my 5-stings have always been my go to instruments. I tried Fender flatwounds on it a while back just to see if I could find a different voice for it, but they seemed kind of uninspiring to me; high tension and not a lot of real tone. This weekend, at the last minute I bought a set of Thomastik flatwounds and put them on this bass. It's difficult to describe the effect they've had on me. Unbelievably HUGE sound. Massive, track filling tone. Since I began playing bass in the early 70's I've always associated flats with dull, lifeless tone. The Thomastik's are ANYTHING BUT lifeless. In fact, they have more tone and life, more personality than any other string I've used - ever. I've repeatedly seen them described as having low tension, being floppy or loose feeling. I didn't experience any of this. Yes, they have less tension that the Fender's they replaced, but they feel SO comfortable under my fingers that they just feel like 'home'.
They impart a very centered tonality that renders a very accurate pitch. They've very neutral tonally. While they do have the above described huge bottom end, they are just equally responsive across the frequency spectrum. In fact, I actually found myself turning the highs down on my Fender - although as they age, I'm sure they'll mellow perfectly.
I've seen Thomastik flats described in almost reverential terms here and in other Forums for a long time. Now I know why. They're amazing strings.