'ere we go...
Note (codex): transport and support stuff such as bikes and landspeeders unrepresented. Those are allocated when necessary.
Corollary (mine): if you want to maximize point values, all assault squads listed would be deployed as bike/landspeeder squadrons, all 6th company deployed as bikes and all 7th company deployed as landspeeders. In case of First Company transports also mean Land Raiders so keep in mind that you can add 10 and more if you want for large increase in total price.
Notes in italics mine and provide the obvious interpretation in game rules. Where a number of units must be split into a non-integer number of formations, it will be rounded to nearest integer.
With the above in mind, the total prices will be pretty much the lower bound of total cost possible.
Chapter CommandMAC, Lord Macragge, Chapter Master -
Supreme CommanderOrtan Cassius, Master of Sanctity -
Chaplain (though might count as an SC too.)27 Honour Guard -
Terminator detachment would be the closest equivalent given that they have very impressive armor and boosted power weaponsLand Raider Maximus -
quite obvious1,700 Chapter equerries and servitors -
unrepresentedApproximate cost: 575ArmouryFennias Maxim, Master of the Forge -
counts as Tank Commander or Librarian27 Techmarines -
Included in vehicle crews95 Tech Servitors -
ditto25 Predators -
6 Predator Detachments8 Vindicators -
2 Vindicator Detachments9 Whirlwinds -
2 Whirlwind Detachments12 Land Raiders -
3 Land Raider DetachmentsApproximate cost: 4250ApothecarionCorpus Helix, Chapter Apothecary -
Commander or Chaplain if you insist12 Apothecaries -
unrepresentedApproximate cost: neggligibleFleet Command8 Strike Cruisers
3 Battle Barges - Octavius, Caesar, Severian
12 Rapid Strike Vessels -
Landing Craft I suppose31 Thunderhawks
Approximate cost: 13050Librarius (not Librarium? my and Matt Ward's dog Latin has failed at least one of us here)Chief Librarian Varo Tigurius -
Librarian, though could make a case for SC5 Epistolaries -
Librarians9 Codiciers -
Librarians10 Lexicaniums -
too wimpy, also shouldn't they be Lexicanii? I don't know!3 Acolytes -
laaaaameApproximate cost: 750Companies - Codex doesn't say that for lack of space in boxes but each company includes a Chaplain (and Captain which they do list separately for each one). Price for those will be always included. Other personnel like Company Champion, Standard Bearer and Apothecary does not concern us.First CompanyCaptain Agemman -
Commander97 Veterans -
Best represented as 5 Terminator formations3 Dreadnoughts
Approximate Cost: 1825Battle CompaniesStructure of those remains almost identical, that is 6 Tactical squads, 2 Devastator, 2 Assault, Captain and (unlisted) Chaplain. Only the number of Dreadnoughts differs.
Second Company has 2 for
total approximate cost of 1225Third Company has 2 again for
total approximate cost of 1225Fourth Company has 4 for
total approximate cost of 1325Fift Company has to make do with only 1 for
total approximate cost of 1175Reserve Companies6th and 7th has 10 Tactical squads which can't be split nicely into Tactical Detachments in E:A

Since They're dual trained in usage of Bikes and Landspeeders respectively, let's say both have 2 Tactical Detachments and 4 Bike/Landspeeder detachments.
6th also has 4 dreadnoughts for
total approximate cost of 16007th also has 3 dreadnoughts for
total approximate cost of 15508th company is all about Assault squads, and will have 5 Detachments of those.
Approximate cost: 9759th company is the same but with Devastators, netting 5 detachments and impressive 7 Dreadnoughts for
total approximate cost of 1700Scout CompanyThis one just lists the captain and says "scout squads". 100 scouts on average doesn't sound too unusual (though it could be closer to 80 at times of war) so let's settle on 5 detachments for
total approximate cost of 975 (without snipers).
So the
lower approximate bound for Total Cost of Ultramarines Chapter or TCUC is
32200 points by the rulebook. It could be stretched to 35000 and beyond by adding Land Raiders, Bikes, Land Speeders and Razorbacks where appropriate.
Whew

That was a long post!