I remember like freshman year i spent $80 on a pair of DKNY jeans cause they were the low kind without the waistband (back when those were really in) and I thought i was so cool because I could afford them and nobody else would spend that much on jeans...I wore them twice.
Therefore I do not buy according to price, i don't even look at pricetags at first. I buy according to taste. If I find a t-shirt that costs 50 cents at GoodWill and I love it, I buy it. If i find a purse for $140 and I love it, I buy it. Don't let prices make decisions for you.
As for the most expensive thing I ever bought, I have no freakin' clue. My pink winter coat was $180...bought i think i've spent more than that before. I dunno.