You can find a 30" BSS, unaltered, for $1500 or less with just a little work. And personally, I would not pay a dime more for one with screw-ins. All my 12 ga. sporting comp guns are fixed choked. But, that's a topic for another thread.
SRH
Seems to me the value of the screw-ins might depend on the uses to for which the gun is intended. For example, if I were to shoot the entire program at the UP SxS Classic with one gun, fixed chokes would not work. There's a sporting clays course (for which you need nothing tighter than light mod at most), two simulated pigeon rings (where you can fire two shots at a bird and may want something tighter than mod for the 2nd shot), and a flurry, where you neither need nor want anything tighter than skeet. Likewise, if you're shooting skeet, sporting clays, and handicap trap with the same gun, the screw-ins come in quite handy. If it's only sporting clays, I agree that you can settle on fixed chokes that will work quite well, especially if you use maybe different loads and shot sizes.
