I haven't been watching the resale market
How many 100 point BCV contracts come up - I take it you are looking for a "less than 150" point contract - those tend to be harder to find, go for a premium and move fast when listed.
If I had that BCV contract right now and I countered at $105 and you came back again with less, I'd tell the broker to drop contact. If you came back and say "oh, ok, $105" I'd say "nope, sorry, you had your chance, I'll take my chances I can find another buyer." Its quite possible that the seller is more interested in negotiating than I would be - its also quite possible that the broker has other offers in the hopper. If you've been watching the market, you will probably have a better idea than I do about the likelihood - how many 100 point BCV contracts are out there? How fast do they move? Have prices stablized or are they still going up ($100 this month or $105 next month - I'll wait for the $105 next month if I'm the seller - I can rent those points this year and see what the market is like next year, I'm not in that much of a rush).
Of course, if the difference between $100 and $105 is what makes the contract affordable to you, you should offer $100 and see what happens.