Surely that's swimming pool fees or subscription? I can't imagine having your own pool is cheaper than a gym subscription.
TBH, gyms have lower prices now over here. You can find a decent subscription for 30€/month, half of what used to be. But they're overcrowded. For me the main factor is time. I end up wasting a lot of time waiting for a free spot or shower, changing clothes, etc. Training at home is much simpler. Combined with a couple of days out swimming or running, a better solution, for me anyway.
Edit: between my previous comment and this one, I've completed my daily home routine :-)