Something I know a little about, I’ve been a keen target recurve archer for the past 10 years shooting for my county over the last 5 and my son is on the GB junior compound squad and has had a few trips in the last 2 years including China and Moscow even winning medals on his last two trips. We are both target but my son is looking at field for his next challenge, my club is mainly field but we do have members that have represented GB in field archery. From what I understand field archery is shot over varying distances at 3 different size target faces, certainly at a competitive level,other forms shoot at animal shaped targets.
Costs, GNAS fees around £50 a year (to join Archery GB for insurance purposes and compete) and club fees vary club to club from £50 upto coiuple of hundred depending. Usually clubs are run by and for their members so not for a profit.
Kit can start from £100 but as everyone will tell you, seek a local club, do a beginer course and take it from there. Many clubs will have a eBay nut who will help sourcing 2nd hand kit. I built my kit up over 5 or 6 years and was somewhat shocked when someone said my kit would cost around £2K to buy new as I’d bought it over such a long time, I dare not add up how much kit my son has.
I’d suggest trying it out a target club, once you are proficient enough to hit the target at a good range of distances then have a go at field, you may soon get put off if you went straight to field and constantly loose arrows in the undergrowth.