The Bridport Prize is one of the biggies with a first prize of £5000 (sterling) for one poem.
Last year though though I spent two days trawling through the massive shortlist trying unsuccessfully to find my name. I've no idea what the total amount of entries was but if the shortlist was 180+, I'd say it had to be 900+.
This year I've been a lot more selective about which competitions I enter. At £6 a poem, it exceeds my limit and I'm not good enough to be picked out of a pot that size. So not for me.
But if you're interested, the closing date is end of June.