I just responded to your other question on a request for best and final offer.
Depending upon the asking price, market conditions, how well the property meets the needs of the buyer, and buyersâ€™ motivation, 90% may be perfectly good offer. If there are other properties which might equally meet your needs and provide a better value proposition for you, then do not hesitate to walk away.
Even in todayâ€™s market, paying 105% of asking price to a highly motivated seller who placed a very low ask price, could represent the best value proposition. Donâ€™t let the % skew your decisions. Let comps, market conditions, and personal value to you and yours guide you.
i.e. Assume an original ask price of 500K, and a seller reduced the ask to 400K. Would it have been better to pay 80% of the original ask? Of 100% of the revised offer price? What if, on this same property, the seller originally went to market with the 400K ask? Would a buyer be making a mistake because they paid 400K?
If you lose the property to another buyer without adjusting your offer at 90%, are you OK with that? Is that your walk away number? If so, then stand on your offer as is. If you would regret losing the property if you stood firm, then consider a revision to your offer.
Best of luck to you.