It can be.
As with most sports, the sky is the limit if you want to spend. If you were to buy all your equipment brand new from premium brands then you could spend £4000+ with a custom made drysuit.
There are good brands that provide better value, plus a thriving market in good secondhand equipment at a fraction of the cost.
You need to be comfortable spending at least £1000 to £1500 after you qualify as an ocean diver.
When diving, your safety is dependent on the reliability of your equipment, so it’s important to know that it’s been looked after and serviced regularly and performs well.