When it comes to charging for infill's all I can say is be strong.
Unfortunately people do like to try their luck and push the boundaries, they will come to you with one or two lashes on and ask for an infill, now me and you both know that this is not an infill it is a full set.
If after you have explained that it is not an infill it is a full set and they still insist that it is an infill then this is exactly what you should give them (an Infill) as after all this is what they have asked for.
Now an infill should be roughly half a set, so this is what you should give them, you have got to remember that this is your time and money, if however you panic and worry that you will lose a client if you don't give them what they are asking for, then they will never pay for a full set again, not only that they will tell all their friends that you can do a full set in an infill time for an infill price and they will never pay for a full set either.
You need to set boundaries from the start have your set prices and what it consists of displayed on your websites or social media platforms, this way people wont argue it with you, after all you wouldn't go into Tesco and tell them you only want to pay for half your shopping so why should it be acceptable to do that with your beautician.
I personally like to have a two week price, a three week price and anything after that is a full set, I also know a lot of technicians charge time they have spent E.G first hour is a set price and then you pay for every extra fifteen minutes after that.
Whatever works best for you, just make sure you get paid for the work you have done ❤️