Nicole, at $25 each you'd soon pay for your matt cutter. I pay about $16-$17 for a full board (32x40") and you can cut 4 matts (note that 40x50 is different to 16x20" so check your frames 1st). My Logan cutter cost about $40-$50 I think but I got a thing called an 'adapt-a-rule' at the same time. It's a ruler with a channel that the cutter runs along, which I think worth the price (was quite dear, and you need the matching cutter). You can use a straight edge but the channel stops you wandering away from the edge. This things aluminium so it's best not to use it to cut pieces of board up as you'll damage it, go to SuperCheap Auto if you have one nearby and buy a steel rule, about 1m long. You also need a self-healing matt, and you can buy them cheap at the Reject Shop (well we can hear in Melb) to ensure you don't cut into your table/benchtop. Use a nother bit of matt board as a cover over the self healing mat to make cutting easier (blade goes thru the matt board easier than the mat).
The best thing about it is you can do weird sizes, and whenever you want them.