These vampire payments add up. £9 a month is £108 per year or about £550 over 5 years plus many people have other vampire payments and they can all add up over time and lead people to debt. I have 4 Amazon accounts and get free prime trials perhaps once a year on each account and that is more than enough for me. I don't find much to watch on prime and I only need free postage around Black Friday etc.
Coincidentally I have need of a 5 metre USB extension lead. I have just looked on Amazon and saw one for £5.99 with a notice that if I spent t total of £25 I would qualify for free delivery. I clicked through to the checkout page to check delivery cost and saw that delivery was free ( I double, double checked that they weren't autorejoining me to Prime nefariously )