I have grown two large-growing pumpkins this year.
I paid £6.90 for 5 seeds of Atlantic Giant. This has grown reasonably well and is about the size of a basketball.
I also bought a 29p packet of Big Max seeds from Lidl.......and this is twice the size of the AG one!
I have fed and treated them both identically.
I have also had great success with other Lidl seeds. Don't be put off by the low price- they are still great quality.
It;'s the wierd thing with AG, they aren't like other squashes adn pumpkins apparently... I know that mine got better treatment than my other stuff this year but until disaster struck they were being seriously outgunned by A Tondo di Padana, a Boston Winter and even a Tondo di Toscana, and that last one is jusst an overgrown ball courgette...... rather meaningless now though.....