LPI20 is the series of the Louisiana Pacific joist. Each manufacturer has different types of I-joist series that have different load handling capabilities. For example, 16" high LPI56's are stronger than 16" high LPI20's.
To give you an idea of price, I just paid approximately $65 a piece for 32' long 16" high iLevel TJI230's.
im guessing that is more expensive than dimensional lumber(i tried to look it up on lowes.com and they didnt show any prices).
with that living room/laundry room wall offset from the center like that, would it cause a problem if i put a girder of 3 2x12's in the middle of the floor with 16 foot long 2x10s, and then just put a basement wall under that living room laundry wall?