What a pain. Coding complex logics in lua is a jigsaw. Don't know how people made a dynamic dungeon scripted in lua? This is torment yourself. Handling the datastore engine has costs me also some time to understand the logic, when server saves it to file. Using the interfacebuilder is also somehow strange, when it restarts full script each time we click a topic. Using the side topics are also limited, because you need to implement an equivalent text and all normal texts are always above the select options. My idea was to put it under the selects. 

But i build something. In relation to all this prisons, it looks not that bad. Currently it can only adjust nrof 1-9 and level 1-9. There is also a strange logic, how to handle the parameters for interface builder. So a diggit (%d) is currently 0 to 9, need to read deaper, how you have implemented %d there or if there is a number for parameters. If not i try string %s for numbers.

But it works, prices goes up by nrof and level. There is no waycheck when buying, i think PickUp handles this and drops to much stuff on ground. I must test this. If player want to buy more, than they can carry, sure, why not. We drop it on ground. No seller says to you, "Ey you can't carry this, i don't sell so much to you."

It's still an early prototyp, need some more fixes. Same link than above. 

%d+ works fine, thx. Script works now with level 1-110 and nrof 1-1000.

I looked deeper in your structures. I always forget that this is server/client coding. So most problems are in client now. Client shows numbers in "select items" fixed from center to right, so 1000 looks ugly over this icon. 999 has also not the best look. And yeah i know you are writing on a new client. Current client has also a problem, when you put a ^hyperlink^ in the description block like this
ib:AddDesc("test ^level 9^") -- hyperlink is broken here, shows empty body when mouse is over link.
And description also goes over the selects. So i need to find a better way adjusting level and nrof with mouse.

With command it works very good now. type nrof 1000, type level 110 and you can buy 1000 level 110 scrolls with one click. I still need to test the weight logic there. But step by step.

I looked client code and had and idea. This side menu for hyperlinks is very strong feature. But currently it's limited to visible hyperlinks. If we allow invisible hyperlinks, we can build cool site menus. It must be not that much on client to change? A kind of clone from ^hyperlink^ build the link, but not showing the text in messagebody? Syntax could be equivalent to ^hyperlink^ like °invisiblelink°. But before i must manage to compile the client. I like coding, but not the environment build "shit" before.

Coding for hypertext in client is here: interface.c line 951