i was told if they look 'bloated' , they should be replaced

i have '4' outside units (3x4t and 1x 2.5t) and last year the a/c co. i use said '3' should be replaced at..... 625bucks.... since the cap's cost around 25bucks, thats highway robbery- i checked em all , and they look ok... not bloated... i mite change em this year.... myself... as its a pretty easy swap...