Well, a few things.
- First, you're going to face an issue if you try to get 100 paintings (even painted by your partner) out of the country using the conventional method. If I recall, an individual is allowed to export annually just ONE work of art/antique. If you export more you'll need to register yourself as an exporter (and yop, that's where the fun begins).
Furthermore, it's likely that in order to register as an exporter, you'll need a CUIT/CUIL, what means if you are here on a tourist visa, that will be impossible.
- Taxes: They are paid directly at Banco Ciudad if I recall (5% of the value, also if I recall) based on their own estimates (in your case, nada/zilch).
- Shipping in PVC tubes -> it's ok for a canvas up to 50x65cm (standard size) but if it's bigger, then the tube itself will weigh more than two kilos. That means you would have to ship from the Centro Postal Internacional and they'll say no of course.
One possible "trick" (quite imaginative... I guess the viveza criolla starts to hit me) would be that your partner, if he has to exit Argentina before you leave the country, reenters Argentina with 100 canvases rolled in a big tube (he could paint those very quickly, just to say "hey! it's Art!". Obviously, you should buy very very cheap canvases in this case since you would leave those here) and get some kind of temporary import document for the 100 paintings. THEN, the day you leave the country, you exit with the real paintings painted by your partner using the temporary import document.
I don't know if my trick is feasible, but in your case, you are not defrauding the Argentinean government or smuggling, you are just trying to take out the paintings painted by your partner (no profit associated to that).
Other than that, I guess you'd need to try to negotiate directly with the Customs here.
Other possibility (first thing to do in fact): Go to Banco Ciudad, Esmeralda 660 --> when you enter the building that's the small office on the right (that's where artworks are to be appraised and it's the first step of the process) and ask them. Likely they'll tell you you need to be registered as an exporter but maybe (crossing my fingers for you) there's some kind of exemption in your specific situation.
I'll keep thinking about your issue. My "trick" might be a viable solution (not sure I should post that on a public forum though... Anyway your intent is not to steal anything so that's ok I guess).
