Amazon's price for a KYB SR4528 Strut-Plus includes Strut, Mount and Spring for $114.87 ... this is the lowest quality complete assembly one can possibly buy. The shop's markup on the estimate is 50%.

According to Amazon, the SR4528, SR4529 front struts and 349185 rear shocks DO NOT fit 4Runners with KDSS or XREAS.

The quote you received is for replacement of all four corners. Personally, I would not buy those struts and shocks. I recommend that you perform the inspection after reading the Gabriel bulletin link in my post above. If the shocks are actually leaking, then I suggest getting another estimate at a well reviewed shop that installs quality parts, such as Bilstein. If you are not going off road, then Bilstein 4600 series is the OEM replacement.