I've recently replaced my wellies, but like others I've gone for rubber.
I needed waterproof, standard height, steel toe, steel midsole, and size 14... Anything above size 11 is internet only!
Got a new pair off eBay for £15 posted, had no issues so far.
As far as expensive vs cheap goes... I used to work in a commercial nursery, working in dry dusty conditions and soaking wet conditions, it didn't help that we put nitric acid in the water. Work boots were really put through their paces, polished or waxed at least once a week. A pair of £100 boots would last 8 months, a pair of £25 boots would last 6 months.