I'll set aside the specific costs of the upgrades for a second and take on the larger issue of the cost increases.
The in-game economy has been dramatically changed since housing was rolled out way back when. Players are much wealthier and have the ability to attain sums of coin much faster than in those early days. Housing to some degree is suppose to be a gold sink, but has long lost that functionality, in that the costs of chests long-since stopped being significant. So in as much as the costs did rise, it's still a once-off purchase. It gets less expensive the longer you average it over, akin to a Lifer sub. That's how I see the increased storage costs.
What I'd personally prefer is having storage upgrades purchasable with gold all the way to the highest tiers (not to the exclusion of TP/MC, but in addition to). But as much as the upgrades cost, it still diminishes over time. If you really wanted to make it a gold sink, you'd increase the upkeep costs, but the effects of that are on an ongoing basis, rather than a once off.
[CENTER][COLOR=#C2C2A3][B]ArcticAurora [/B][COLOR=#999966]95 S/B Guard[/COLOR] [COLOR=#ffffff][B]//[/B][/COLOR] [B]Pavello[/B] [COLOR=#999966]95 OP Guard[/COLOR] [COLOR=#ffffff][B]//[/B][/COLOR] [B]Canadian[/B] [COLOR=#999966]95 Capt[/COLOR] ... [SIZE=1]et alts[/SIZE] [/COLOR]
[B][SIZE=2][COLOR=#C2C2A3]2013 Player Councillor[/COLOR][/SIZE][/B] [B]//[/B] [SIZE=2][COLOR=#C2C2A3]Rich people would rebuild the Bridge of Khazad-Dûm. Wealthy players fill the great chasm with gold.[/COLOR][/SIZE]