KMS sets pricing

When i pay for a KMS set, i wonder what would be the best idea to write down the price i paid for it.
Lets say i paid 40euros for Vatican kms 2008. 8 Euro coins.
I want to have the price recorded in my Numista collection. If i write it as a remark, it won’t reflect my collection value. If i put the 40€ on one coin like the 2€ , it will wrongly participate in calculating the Numista estimated value of this coin, if i understand it correctly.
What i do is try to find the estimate values for each coin of the set ( not always each separate coin has value estimate on Numista) . Sometimes i have to look up in other catalogs . And the prices between the catalogs differ significantly. If the total of separate coins sum up to 80€ and i paid 40€ , then i write down on each coin 50% of the catalog value for each saparate coin.
As sets are not managed in Numista, so aren't set prices. Official sets might have more value as separate coin values.
It would be interesting to read what do other Numista members with this issue.

I use Fibonacci numbers for my San Marino sets:
1 cent = 1;
2 cents = 1;
5 cents = 1+1 = 2;
10 cents = 1+2 = 3;
20 cents = 2+3 = 5;
50 cents = 3+5 = 8;
1 euro = 5+8 = 13;
2 euros = 8+13 = 21;
5 euros = 13+21 = 34;

The sum of all these numbers (1+1+2+3+5+8+13+21+34 = 88) equals the price you've paid for the set, let's say, 50 euros.

Then, each coins value = coin Fibonacci coefficient * (price you've paid / sum of coefficients):
1 cent = 1 * 50/88 = 0.56
2 cents = 1 * 50/88 = 0.56
5 cents = 2 * 50/88 = 1.12
10 cents = 3 * 50/88 = 1.68
20 cents = 5 * 50/88 = 2.8
50 cents = 8 * 50/88 = 4.48
1 euro = 13 * 50/88 = 7.28
2 euros = 21 * 50/88 = 11.76
5 euros = 34 * 50/88 = 19.04

You can then round the values to make them nicer and get something like:
0.5, 0.5, 1, 2, 3, 4, 7, 12, 19 = 49 which is very close to truth.

This approach is not a silver bullet, yet I like it. Of course I'd prefer that Numista would provide a possibility to add sets right away :)

Have to admit, this is very interesting way, i didn’t think about.
Will consider to adopt it.

This the slight flaw of having proof sets! Also interested how people do it. I put it in the private comment at the moment something like £40 for 2020 year set.