Well, while you may feel for-material-costs work doesn't obligate you to be fully professional, the reverse is true for the client. They aren't really out anything if they decide to drop the project. Do you make your clients sign contracts or read over a TOS before you start? I'm guessing no since you said they were friends, but this would be my first suggestion.
"I know he'll pay me back for what has been spent" --> So you are saying that you buy the materials before getting any money from your client? You may want to consider having a... either deposit or down payment, the nonrefundable one (I don't want to say the wrong word) to cover the cost of materials. If you decide to charge extra for labor after that or not, or add an extra kill fee on top, would be up to you. Of course, if you took forever on the project, the deposit (?) would be void since you would be breaking the agreement in that case. Being slow is fine as long as you are upfront about it and the client is aware you are making progress, though. But if you take years and the client wants a refund, they should get a full refund imo. Its unclear from your post if that is the case in this current situation or not.
As for what to do about your current dropped project, I had two ideas if you are interested in hearing them.
1. If the costume is not too size-dependent, finish it and offer it for sale as a pre-made item.
2. If the costume requires specific sizing, offer up a commission slot where someone pays you to finish making the costume for them. You already have the materials and patterns ready to go, they just send you their measurements. You'd want to get some sort of TOS made up before you do this, making sure to point out how much if any customization you are willing to do for the new client.
Those ideas may not work for you, but if they do they would let you be atleast somewhat compensated for the work you already put in.
no subject
"I know he'll pay me back for what has been spent" --> So you are saying that you buy the materials before getting any money from your client? You may want to consider having a... either deposit or down payment, the nonrefundable one (I don't want to say the wrong word) to cover the cost of materials. If you decide to charge extra for labor after that or not, or add an extra kill fee on top, would be up to you. Of course, if you took forever on the project, the deposit (?) would be void since you would be breaking the agreement in that case. Being slow is fine as long as you are upfront about it and the client is aware you are making progress, though. But if you take years and the client wants a refund, they should get a full refund imo. Its unclear from your post if that is the case in this current situation or not.
As for what to do about your current dropped project, I had two ideas if you are interested in hearing them.
1. If the costume is not too size-dependent, finish it and offer it for sale as a pre-made item.
2. If the costume requires specific sizing, offer up a commission slot where someone pays you to finish making the costume for them. You already have the materials and patterns ready to go, they just send you their measurements. You'd want to get some sort of TOS made up before you do this, making sure to point out how much if any customization you are willing to do for the new client.
Those ideas may not work for you, but if they do they would let you be atleast somewhat compensated for the work you already put in.