just re-read your post, and realized the prices vary, so the discount would vary. oops.

based on items with specific value
total of PRICE where PRODUCT-TYPE has a vlaue of TYPE1 minus 50.

so - it the total of the price column for the 10 items that are TYPE1 is \$96, then minus \$50 would make the discount \$46 - thus leaving the customer payng the \$50.

problem is this will only work for 10 items.
11 items would cause chaos because they would get 11 for \$50 too.

Another idea would be to make the shirts FREE and then adding a CHARGE.
so the bottom rule would be
based on items with specific value
Total of PRICE where PRODUCT-TYPE has a value of TYPE1, times 1.
(this is giving the total price of TYPE1 products as a discount)

then add a charge rule that is
based on the nubmer of items with a specific column value
if the total number of items where PRODUCT-TYPE has a value of TYPE1 is > 9
and the bottom:
based on items with a specific value
total of QUANTITY where PRODUCT-TYPE has a value of TYPE1 times 5.

this idea will give any quantity 10+ for \$5 each.
but its too bad it would have to show up as a discount and a charge.

LAST IDEA
you could hand code some of this. the only PITA is that if you hand code it, it could get overwritten anytime you open up your ecart editor wizard. i have handcoded a variety of the coupons that i couldnt get the wizard to create.