One of my biggest customers is a print broker. She used to be a sales rep for a print company, then they shut down...and she started her own business where all she does is be a broker between her clients and someone else. So she had a leg up and already has a ton of clients... Not just stickers, but signage as well as banners / stickers / she even started to hire me to do kiosks.
The margins aren't as great as if you're doing it yourself... but then you're also not dealing with clients and handling all the artwork and other things, so it's kind of a win win. I have a certain SQFT price for her - She doesn't even ask me how much, or to quote on things anymore... just sends me art, asks when it'll be done, and pays the bill. I just checked and she's done 70k alone with me this year... and it's usually high margin stuff for me like decals / installs / coro signage that costs me nothing... I just print her stuff overnight and be done with it, so it's like a "bonus".
My work absorbed a sign shops production - They make ALL the signage for all the parking lots here...and they closed down their western office. We sell to them at a set SQFT price - It pisses me off when we get an order for a 2" Decal and its like a 50 cent order... we lose money on those, but theyv'e also done over 200K a year with us this year - Theyre happy...we're happy, and its led to us getting some other work ontop of the parking work.
I'm not saying drop your price so that its not worth it - But inquire if there will be other work, or if its just a one off. If you're sure theyre not selling to your clients and undercutting you... Then it can be a beneficial relationship. If they go after the same people you are though... obviously not worth it.
Treat them like a sales rep that you don't have to pay
And don't drop your price in half... Give them 15-20% off regular price... Then they make some cash making the sale, and you aren't just trading hours for work.