Trapper - Wolff - one spring is $7.89 (you will probably get one firing pin spring with it).
Calibration pack is $31.49 and has 5 recoils (one of each #) and three firing pin springs.
Depending on what you mean by "buy one of each" - your break-even is 4.
Seeing that Wolff makes a 22# (not included in pack), maybe that is what you have. If so, and if you shoot a lot, wouldn't hurt to have a back-up.
If pistol was alloy frame, I would not recommend 14# recoil. Since your 5906 is SS frame, maybe you'll want a 14# along with whatever others you choose.
Run the shipping costs also - I bought 2 recoils - shipping was $3.99. It may be flat rate for such light items.
Either way, probably better to buy all you might want at same time.