Shock/strut replacement (how many need replacement)

What is your question?

Mechanic says I need to replace shock/strut and need a stabilizer bar kit. Total cost for job is about $900. My understanding is that there are two(?) shock and struts (4 in total). Will they have to replace all 4 at one time or could it be they meant one shock, one strut (the estimate looks like they are charging for one of each rather than both for back and front).