Again, the most expensive part in the project. The casters.
What do i usually with old pallets?
Last time, believe it or not, i used it as a pallet.
The time before that, i used it to fir out walls when rebuilding a bath / shower.
½" thick wood just sitting there. and it just so happened that i needed to fir out the wall ½".
And, about your project. Worse comes to worse, you can feed it to your rocket stove.
Yes the casters would be worth a lot. I can't remember where they came from but I got them fro free somewhere and they sat in my garage for almost 10 years!
After making this I saw a YouTube where a guy made a desktop from pallet wood, added some metal legs and sold it for over $1,000!