My friend does exactly this between IKEA and Ebay. Here in Australia, IKEA does not ship (not sure if they do else where) so she buys a heap of items at the Ikea stores and flips them online. She's been doing it for years and does pretty well at it. Here in Australia, IKEA stores are few and far between so her arbitrage is a huge value add for a lot of her customers since IKEA cannot (won't?) ship and traveling X KM'…
Ikea here in singapore just started doing delivery 2 months ago.
If you purchase in store hey do delivery, but the queues can be an hour on the weekends.
They have services like GoGoVan to get some bulky items home cheaper.