Some Sales professionals consider when they get an invitation from the customer to negotiate, they have reached 90% of the sales cycle. Do you agree?

not necessarily it depends on the buyer behavior and procedure of buying. Some companies in B2B business that have centralized procurement they negotiate with all suppliers to get the best offer that suits them, then it will be awarded. 

In general, NO

There's sign from the customer >>offer the after sales services & close the deal

There's no sign (100%) >> apply the customer journey philosophy

Getting an invitation to negotiate is a good sign but there still be a lot of work to be done,an invitation to negotiate means the customer has many unresolved issues that must be resolved before committing to a sale.

I’ll agree to disagree! Let me Explain.

An invitation to negotiate is clearly a request to give something, if you are the one and only decision maker, that maybe your90%.

Though you be faced with an unexpected wager to give at the negotiating table that may supersede your authority therefore % is unknown.

May be this will provide promising chances, but90% is too much

No

Depends on product line… If it’s about real estate too than negative.

yes

I agree......

as invitation to negotiate has a very high attraction towards finaizing a deal,

BUT depends upon the buyer's research, having quotes and personal approach towards choosing the lowest offer

WELL on a side its purely favourable as if we have always some cushion to bare the pricing factors & power of decision.

ALSO depends on nature of Product, if its on manufacturing/retail side, chances are higher to get a deal. 

no do  not  agree  since some customers are  nothing  but  information collectors , so  they will call you   just to have  the  information then doing  nothing. some sales invitations are  failed even at the  100% stage .thus sales are  done only after  customers paid and acknowledged .

Not really. Sometimes customers negotiate so they can take it to other competitors and ask them to better the offer.