I have a 98 V70 T5 with 120k mi. and have noticed this crashing/banging problem on lousy roads. I think it's due to a combination of stiff suspension, low profile tires & possible defective spring seat. If you hit a pothole hard enough, you'll actually compress the low profile tire all the way to the rim, thus the crash/bang sound & feel. You can also dent a rim. One disadvantage of low-profile tires.

Since you have 17" wheels, I would guess that would make it worse.

I still have the original OEM struts at 120k mi. but just fixed a loose pass. side spring seat. It was knocking pretty hard over low speed bumps. A way to test this is to raise the hood, grab the top of the strut (the ~3" round metal disk) and see if you can twist it. If you can, the spring seat is history. Also, pull it from side-to-side, there shouldn't be any movement whatsoever. If this is loose, it will bang around everytime you hit a pothole, generating noise.

Finally, the cost of your repairs does seem quite high to me compared to central Tx. Then again I've heard everything costs more in SoCal.
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1998 V70 T5 110Kmi; Previous car: 1985 SAAB 900T, 254kmi