Problem with upgrading is the eventual cost. But the problem with a new bike is that it will have a few "Price" compromises fitted to it to keep the price down. Some of those compromises will not matter but some do. Heavier components for one thing will always keep the weight up and unless you have a stock of lighter parts already- then the bike will stay heavy. Thinking of Handlebars- stems- Cranks etc. The other thing they downgrade is the wheels. Not exactly a downgrade but to keep the price down- a cheaper set of wheels are fitted.

Within Your "Budget"- and mine- those cheap- heavy items have to stay on the bike till you "Upgrade". Or do they?

I buy Frame and Forks for the serious bikes now and get them built up to my spec and my budget. That way I can get the compact crank fitted that is good- the right bar and stem size and more importantly - the good wheels. But when you buy a bike- it is possible to get the shop to change the parts to something better. They will be able to sell them from their stock and they make an allowance for the parts.

Last bike I bought though was one built up by the shop. It had cheap Giant wheels fitted and I did keep them as I have a use for them. but I also negotiated a price for a good set of wheels to go on it aswell.