Here's a random example:

SFO/ANC - In one fare class (in this case, Y), it prices as a thru fare, connection be damned.

SFO AS X/SEA AS ANC 809.05YH0OASMR USD809.05END ZP SFOSEA
FARE USD 809.05 TAX 5.60AY TAX 34.55US TAX 9.00XF TAX 9.60ZP
TOT USD 867.80

In a different fare class (in this case, X), it prices by segment.
>SFO AS SEA 87.44QH2OASBN AS ANC 94.21GH2YCUBN USD181.65END ZP
SFOSEA
FARE USD 181.65 TAX 5.60AY TAX 15.98US TAX 9.00XF TAX 9.60ZP
TOT USD 221.83

Sometimes AAA/BBB/ and BBB/CCC are cheaper than AAA/BBB/CCC, and when booked together, they'll price as the AAA/BBB + BBB/CCC and not as AAA/CCC (or in the case of a RT that will only price as a RT, very rare on AS), it will price as AAA/BBB RT + BBB/CCC RT (all on the same ticket - but the most restrictive segment's fare rules will apply).