I feel the same way mostly, but I'm considering upgrading the memory from 2GB to 4GB. Having to buy a new computer more and more frequently would end up costing a lot too. Paying an extra $100 now isn't going to future proof my mac, but maybe it will keep it relevant for an extra year. The question isn't whether I want to spend money or not, it's whether spending a little more now will save me a little more down the road. Here's a generalized example:
I can spend $1,000 every three years on a new base macbook, or spend $1,100 every four years. After 12 years, the first option will cost me $4,000, while the second option will only cost me $3,300.