Part of your question is to find the threshold price of a crafted item that covers exactly its cost of production, especially when production is random. Once you know this threshold, the price you will ask to a buyer has to be greater than this threshold. Otherwise, you make losses.
Consider the craft of a precise item.
First, you need to determine a value for each item that enters as inputs. The sum will be denoted $V_I$.
If you do not have any idea about the values, you can set them as average market prices, so that $V_I$ is the average market price for all the inputs. In other words, $V_I$ is what it costs you to produce the item if you have to buy the inputs on the market.
If there were no randomness in production, you would ask at least a price $p\geq V_I$ to any buyer who does not provide you with any input. Conversely, if the buyer comes with all the inputs, you have zero cost and your constraint is simply $p\geq 0$. If the buyer comes with some inputs, the price should be higher than the value of the remaining inputs.
It becomes more difficult with randomness in production.
You need to determine two elements: i) the probability $q$ to fail in producing the item, ii) the value of non-desirable outcomes $V_N$.
You can estimate $q$ by dividing the number of times you failed by the number of times you tried.
If the non-desirable outcomes are not always the same, $V_N$ can be an average. Again, if you do not know which value to associate, you can take average market prices. In that case, $V_N$ would be on average the money you get from selling the non-desirable outcomes on the market.
There are two possibilities. Either you make the buyer bears the risk, or you cover the risk.
In the first case, imagine for instance that you manage to produce the desirable item after 3 trials. The price you will ask to the buyer should be at least $3V_I-2V_N$ because you needed 3 times the inputs but you will keep twice non-desirable outputs.
Whether a buyer is lucky or unlucky, it is not your problem. However, you do not have an invariant price of the crafted item.
In the second case, you can ask a fixed price to the buyers (higher for non-members), irrespective of their luck.
If you make enough transactions, the lucky buyers will pay for the unlucky ones, and you can make positive profits at the same time. We need some maths to find the expected (or average) cost of producing the item. The average cost is the sum of the values of inputs minus the values of non-desirable outcomes, weighted by the probability of each event.
$$AvCost = \underset{1\ trial}{\underbrace{(1-q)V_I}} + \underset{2\ trials}{\underbrace{q(1-q)(2V_I-V_N)}}+\underset{3\ trials}{\underbrace{q^2(1-q)(3V_I-2V_N)}}+...$$
This writes as
$$AvCost = (1-q)\sum_{k=0}^\infty q^k[(k+1)V_I-kV_N].$$
Using $\sum_{k=0}^\infty q^k(k+1)=\frac{1}{(1-q)^2}$, we obtain
$$AvCost=\frac{V_I-qV_N}{1-q}.$$
The condition to make positive profits on average is to fix a price $p\geq \frac{V_I-qV_N}{1-q}$. In other words, if you want to be the most generous with members, they have to pay at least $\frac{V_I-qV_N}{1-q}$ so that you make no losses on average. If a buyer comes with some inputs, you reduce this cost by the value of her inputs.
Members vs non-members
You can also decide to make losses on average for your members, $p_{member}< \frac{V_I-qV_N}{1-q}$. These losses would be compensated by gains from non-members, $p_{non-member}> \frac{V_I-qV_N}{1-q}$. You have to make sure that the gains compensate the losses.
About being competitive on the market
We have established the conditions to make positive profits, but there is no guarantee that you will be competitive on the market. It is possible that the minimum price you ask to a buyer ($\frac{V_I-qV_N}{1-q}$) will still be higher than the price of your competitors. They can produce the inputs more easily for instance, or they can value the fact that the skill to produce will level up.