Although I've had fairly good luck with Olfa's lasting several years, I'm switching over to Martelli. Twice a year they have a special on all of their products, 50% off. That makes them pricey instead of astronomical.
Until you actually use one and feel how different they are, it's hard to explain. They have an almost "soft" feel. Don't warp, regardless of being in sun, car, etc. Even when cutting minky or fleece, I've never had fuzzies that I get on my Olfas.
I have a larger one that I keep on my cutting table, and a smaller one (18 x 24) next to my sewing machine. Although I haven't tried it, their youtube video says you can actually iron on it, as long as the iron doesn't come in direct contact with that mat.
If you want to get their redline specials, when you go to their website, scroll down menu on left. You must go to redline direct, not just their e-mail listing. Sign up for redline direct. Once a month they have deep discounts, usually on a specific product. Twice a year (July and December) they have 50% off of everything; this is when I make my purchases.