By Christopher Tan, Senior correspondent

IT HAS been a roller-coaster week for some car buyers.

Those who booked a vehicle as far back as January and have yet to take delivery of it have been asked to 'top up' what they paid to secure certificates of entitlement (COEs), prices of which jumped by up to 50 per cent in last week's tender.

Another group of buyers, however, breathed a collective sigh of relief, having collected their cars before the big price hike.

At Toyota agent Borneo Motors, salesmen have asked their customers to fork out between $8,000 and $11,000 more.

Operations director Chan Eng Siew, 48, feels hard done by.

He booked a Toyota Vios at $52,888 on Jan 4, and was told he would get the car only this month or the next.

But though there were six COE tenders held between then and now, Borneo Motors made only one bid for him and was unsuccessful.

Now, Mr Chan has been asked to pay $8,000 more if he wants the agent to continue bidding for him, and $11,000 more if he wants a 'guaranteed' COE.

The alternative? Void the sale and get his deposit back.

But he would still end up paying more for a car now if he goes for an equivalent make as prices have spiked along with the cost of COEs.

Mr Chan said: "I feel it's unfair. Why didn't Borneo bid when premiums were more stable?"

Another Toyota customer, teacher John Low, 63, said Borneo Motors failed to bid for a COE for him.

He has sold his current car and must hand it over to its new owner next month.

The fact that he was actually 'quite happy' with his car, but had been attracted by Borneo Motors' $6,000 discount campaign last December, adds to his pain.

"I'm at the losing end," he said.

A spokesman said Borneo Motors usually spaces out its bids to avoid sharp rises in premiums: "For most customers, we tried to bid but were not successful. Those for whom we did not manage to bid at all - they belong to a very small group."

He added, however, that customers who agree to fork out the extra $8,000 to $11,000 would still be paying less than one who books a car now.

The Vios, for example, now costs about $71,000 - $18,000 more than it did in January.

But this is cold comfort to those buyers who feel that Borneo Motors should have secured COEs when the premiums were much lower.