Yeah, getting to 11,000 is rediculously expensive...
Yeah, particularly when you add 1000 lower tier seats at a time!!!!
You have a CRAZY amount of LT seats now . . . my recommendation (for what it may be worth) would be to add nothing but bleachers after this addition until you get to 13K bleachers. Bleachers go for $13 or so at D.III . . .