Bundle from same keyword in one category

Hi,
I am building an ecommerce site to sell photos of events, typically sports, where people search their photos by bib number (which is a keyword inserted in the product). I’ve been struggling with a particular condition for a while now, and I think this plugin is the right one to solve it, but I haven’t managed to work my way through it exactly. I would be very thankful if I could get some help.

As a marketing technique, I want to sell, let’s say, “1 PHOTO” for 5€ and “ALL YOUR PHOTOS” for 10€ (“all your photos could be 2,3,4,5… depending on the person, it’s not a fixed quantity). That way people will go for the entire pack, and because the photo is already made, it’s no extra production cost.

So I want that if someone puts all their photos in the cart, the price will be 10€.
The condition should be something like (and I am no coding expert, so I’ll just put it this way):

IF keyword=X IN category=Y THEN price=10€

(it’s okay for me to build a rule for every new event because price may be different, but I can’t create a rule for every single bib number because we are talking about thousands of participants).

Also, it’s important that this condition only works out if the keyword is the same throughout all the products, not allowing someone to buy photos of two different persons in the price of the bundle, then it should be two bundles. Also, I don’t want to make it possible toinclude products from other categories into it, because there could perfectly be another bib number 51 or 123 or whatever in another event.

I know the request is a bit complicated, and I have tried to explain it in the best way possible. Thanks in advance for any help.