i think once you get going and get use to it you can get alot more then you think! i reuse the same bit of foil for my top and bottom lip and do it in sections if there is a gap on the foil from the other lip, if there is gaps i put some more prime on and then apply the foil again!
Most people are finding they retail really well instead of doing it as a in salon treatment the RRP is £29.95 and you should get 30 applications per tube
maybe try using less look at the bit your about to throw away? can you get another application from it?
a good idea is to do a set on a client and then they buy the packet that you've just used on them and they get the application half price/free depending on how nice you are

haha x